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7/27/2014 9:00 P.M. ET

Prospects reshuffle in Athletics' updated Top 20 list

Class A Stockton shortstop Robertson tops Oakland's farm system at midseason

With the passing of the Draft signing deadline, teams have had a recent influx of talent into their farm systems, and with that, we've updated the Top 20 Prospects lists of all 30 teams.

To be on a list, a player must have rookie eligibility. To qualify for rookie status, a player must not have exceeded 130 at-bats or 50 innings pitched in the Major Leagues, or accumulated more than 45 days on the active roster of a Major League club or clubs during the 25-player limit period, excluding time on the disabled list or in military service.

Players are graded on a 20-80 scale for future tools -- 20-30 is well below average, 40 is below average, 50 is average, 60 is above average and 70-80 is well above average.

Check out all 30 team Top 20 lists and the Top 100 on Prospect Watch.

1. Daniel Robertson, SS
Preseason rank: 3
MLB Top 100 rank: 92 (Preseason: NA)
ETA: 2016
Scouting grades: Hit: 55 | Power: 50 | Run: 40 | Arm: 55 | Field: 50 | Overall: 55

Addison Russell is not the only quality shortstop prospect the A's landed in the 2012 Draft. With the club's second choice, at No. 34 overall, Oakland grabbed Robertson, and it signed him for $1.5 million. Robertson is not as electric as Russell (since traded to the Cubs) -- few shortstops are -- but Robertson profiles as a fine hitter who could stick in the middle infield.

Robertson's best tool is his bat. With a short stroke and an all-fields approach, Robertson makes consistent line-drive contact. His hitting acumen, bat speed and strength should give him high-producing power down the road.

Though Robertson is a below-average runner, he can make plays at shortstop thanks to his arm strength and his instincts. His ability to read balls off the bat gives him deceptive range, and he might have the softest hands in the system. If Robertson has to move, his bat will still profile well at second or third base.

2. Matthew Olson, 1B
Preseason rank: 5
ETA: 2016
Scouting grades: Hit: 45 | Power: 60 | Run: 30 | Arm: 55 | Field: 50 | Overall: 50

A highly regarded two-way player coming out of high school in 2012, Olson was selected in the compensation round. The A's made him a full-time hitter, and Olson showed why in 2013. He ranked second in the Midwest League with 23 home runs as a 19-year-old. Olson has shown even more power this season in high Class A.

Olson has a quick and easy swing that gives him the potential to hit for average as well as power. His swing does have a tendency to get long, making him prone to strikeouts.

Olson is a well-below-average runner, which contributed to the A's moving him across the diamond from his high school position of third base. Olson has good hands and he looks like he could develop into an excellent defensive first baseman.

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3. Renato Nunez, 3B
Preseason rank: 6
ETA: 2016
Scouting grades: Hit: 45 | Power: 55 | Run: 30 | Arm: 55 | Field: 40 | Overall: 50

The A's had an all-prospect infield at low Class A Beloit in 2013, with Olson at first base, since-traded Chris Bostick at second, Robertson at shortstop and Nunez at third. Nunez ranked fifth in the Midwest League with 19 homers, more than doubling his total of nine from his first two seasons in Rookie ball. Nunez has continued to drive the ball in high Class A this year.

Signed for $2.2 million out of Venezuela, Nunez presents a combination of tantalizing and raw tools. He has a sound and quick right-handed swing, and he can drive the ball to all areas of the field -- though he also can get himself out by being overly aggressive at the plate. If Nunez can adopt a more disciplined approach, he could produce for both power and average.

Though Nunez's strong arm fits at third base, it's uncertain whether he can remain at the hot corner in the long run. Nunez's hands and feet need a lot of work, and if he can't cut it at third, his well below-average speed may mean that first base is his only other option.

4. Matt Chapman, 3B
Preseason rank: None (2014 Draft)
ETA: 2017
Scouting grades: Hit: 50 | Power: 55 | Run: 40 | Arm: 70 | Field: 60 | Overall: 50

Oakland has had five first-round or supplemental first-round picks in the past three Drafts, and the club has spent four of those picks on infielders. The latest infielder selected was Chapman, who wowed the A's in a workout shortly before the Draft. He went 25th overall and he signed for $1.75 million.

Chapman fits the third-base profile to a tee, as he possesses the power potential and arm strength teams want at the position. Chapman manages the strike zone well, and while he can be inconsistent at times, he's doing a better job of turning his batting-practice power into home runs during games.

Chapman has Gold Glove upside at the hot corner. He moves well at third base and he has a cannon of an arm that has produced fastballs up to 98 mph in limited stints on the mound. Chapman is reminiscent of Michael Lorenzen, another Cal State Fullerton star who gave up playing the outfield to become a full-time pitcher after the Reds made him a supplemental first-round choice in 2013.

5. Dillon Overton, LHP
Preseason rank: 8
ETA: 2017
Scouting grades: Fastball: 60 | Slider: 60 | Changeup: 50 | Control: 50 | Overall: 50

Though Jonathan Gray went No. 3 overall to the Rockies in the 2013 Draft, it was Overton who opened that college season as Oklahoma's ace -- and was regarded as the better prospect of the two. Overton wound up straining his forearm, but he pitched through the injury with reduced stuff. The A's took him in the second round, and when they discovered that he would need Tommy John surgery, they were able to sign Overton for $400,000.

When healthy, Overton can show three plus pitches. Overton deals in the low 90s, and he can hit 95 mph with a fastball that gains deception and life from his crossfire delivery. Overton can make batters look bad with his slider, and he can also get swings and misses with his changeup.

Overton has plenty of polish, too, and he's also mentally tough. Overton returned to the mound in late June, and he could prove to be a steal for Oakland.

6. Chad Pinder, 2B 
Preseason rank: 18
ETA: 2016
Scouting grades: Hit: 50 | Power: 45 | Run: 50 | Arm: 60 | Field: 45 | Overall: 50

Pinder drew comparisons to Evan Longoria while starring in the Cape Cod League in the summer of 2012. While that's a stretch, it does speak to Pinder's all-around ability. As a bonus, he may be able to play the middle infield.

Though Pinder had a lackluster pro debut, he has the hand-eye coordination and bat speed to hit for a solid average. Scouts are more mixed about Pinder's power potential, but he can drive the ball to the opposite field. Pinder should be good for at least double-digit homers on an annual basis. 

Pinder has the hands and arm for a shortstop, where he played primarily in his pro debut -- though he moved to second base when he joined Robertson at high Class A Stockton. Pinder profiles best at second, which would require less power than a shift to third base.

7. Raul Alcantara, RHP
Preseason rank: 4
ETA: 2017
Scouting grades: Fastball: 60 | Slider: 50 | Changeup: 60 | Control: 50 | Overall: 50

Trading Andrew Bailey and Ryan Sweeney to the Red Sox in December 2011 has worked out well for the A's, who received Josh Reddick, corner-infield prospect Miles Head and Alcantara in return. Alcantara had a rough first season in his new organization, but he bounced back in 2013 to assert himself as the system's top pitching prospect. Unfortunately, Alcantara injured his elbow in the spring of 2014 and he had Tommy John surgery in May.

When healthy, Alcantara usually operates at 92-93 mph with his fastball, and he can reach 96 mph. Alcantara has done a fine job of refining his changeup in his two years in Oakland's system, to the point where it now ranks as his second-best pitch. His hard slider can also be a weapon at times, albeit with less consistency.

Scouts who saw Alcantara in low Class A in 2012 and '13 noted his improved mound presence the second time around, as he learned to trust his stuff and attack hitters. His control and command took a step forward, and if Alcantara continues to improve, he could be a No. 2 or 3 starter.

8. Seth Streich, RHP
Preseason rank: None
ETA: 2016
Scouting grades: Fastball: 60 | Curveball: 50 | Changeup: 45 | Control: 50 | Overall: 45

Streich was a two-way player at Ohio, where he had more consistent success as a first baseman/DH than he did as a starter. But scouts thought Streich's future was brighter on the mound and that he'd fare better once he focused solely on pitching. Thus far, scouts have been correct on both counts.

A sixth-round pick in 2012, Streich missed the end of his first full pro season with a balky elbow. He came back healthy and he is throwing harder than ever this season. Streich is working in the low 90s, and he regularly touches 95 mph with his fastball. The hard sink on his heater makes it difficult for hitters to drive.

Streich is working on refining his secondary pitches, though his curveball and changeup show glimpses of becoming solid offerings. Streich throws strikes, but he needs to do a better job of locating his pitches within the strike zone. He has a ceiling of a No. 4 starter, and he could also develop into a useful reliever.

9. Max Muncy, 1B/3B
Preseason rank: 15
ETA: 2015
Scouting grades: Hit: 55 | Power: 50 | Run: 40 | Arm: 45 | Field: 45 | Overall: 45

Coming out of Baylor in 2012, Muncy's patient approach at the plate made him the kind of advanced college hitter that the A's have become known for drafting. Behind a power surge that saw him hit 25 home runs between Class A Advanced Stockton and Double-A Midland, Muncy has taken a step forward in his first full season.

Muncy will have to prove the home runs weren't just a California League mirage, but he has always had solid pop waiting to be unlocked. In addition to his power, Muncy has excellent pitch-recognition skills and remains adept at working walks.

Muncy is more athletic than his frame suggests, and he is an adequate defender at first base. Oakland has given him some time at third base in 2014, but that's a stretch for him to play there on a regular basis. Muncy earns high marks for his makeup and understanding of the game.

10. Bruce Maxwell, C
Preseason rank: 17
ETA: 2016
Scouting grades: Hit: 45 | Power: 45 | Run: 20 | Arm: 50 | Field: 45 | Overall: 45

Maxwell led NCAA Division III with 15 homers and a .918 slugging percentage in 2012, when the Athletics made him the highest-drafted D-III player in nine years by taking him 62nd overall. Maxwell's production hasn't been as gaudy as a pro, in large part because he has devoted so much energy to refining his catching skills.

While Maxwell hasn't tapped into his plus raw power, his sound approach hasn't wavered. Maxwell works counts and he focuses on driving the ball from gap to gap. The A's think he'll step up his offense, as his defense becomes more second nature to him.

Oakland credits former big league catcher Marcus Jensen for helping Maxwell improve behind the plate. At 6-foot-2 and 235 pounds, he's not the most agile backstop, but he has made strides with his receiving. Maxwell has raw arm strength, but he needs to smooth out his throwing mechanics to better combat the running game.

11. Bobby Wahl, RHP
Preseason rank: 7
ETA: 2016
Scouting grades: Fastball: 60 | Slider: 55 | Changeup: 50 | Control: 45 | Overall: 45

After turning down seven-figure offers from pro teams as a high schooler, Wahl went to Mississippi, and he entered 2013 as a possible first-round pick. But blister issues led to diminished stuff, and his signability concerned clubs. Oakland stole Wahl in the fifth round and signed him for $500,000.

Wahl's fastball velocity bounced back after he turned pro, ranging from 90-95 mph. He has reached 97 mph in the past while coming out of the bullpen for the U.S. national college team. Wahl's hard slider also regained its sharpness, and he also continued to exhibit feel for his changeup.

Scouts aren't enamored with Wahl's delivery, and they wondered if the effort he expends will lead to him becoming a reliever. It's hard to argue with Wahl's track record of success against top college competition in the Southeastern Conference, though he has struggled in his first full pro season. The A's hoped he could move quickly through the Minors and become at least a No. 3 starter, but it appears that was optimistic.

12. Nolan Sanburn, RHP
Preseason rank: 10
ETA: 2016
Scouting grades: Fastball: 60 | Curveball: 60 | Slider: 50 | Changeup: 45 | Control: 45 | Overall: 45

Sanburn has less mileage on his arm than most pitching prospects. He was better known as an outfielder in high school, and he worked just 73 innings in two seasons as a reliever at Arkansas. Signed for $710,000 as a Draft-eligible sophomore after being taken in the second round in 2012, Sanburn pitched just 48 2/3 frames in his first two seasons as a pro, after a shoulder strain sidelined him for most of last year.

Sanburn was healthy again at the end of the season. In instructional league, he was back to throwing 93-95 mph heat. Sanburn reached 99 mph as a college reliever, and he can throw his fastball by hitters up in the zone. His low-80s curveball has good depth, and it gives him a second power pitch. Sanburn can also display a tight slider and a sinking changeup, giving him more than enough options to start.

Because of concerns about Sanburn's command and durability, Oakland has decided to move him to the bullpen. His ability to locate his pitches and keep his pitch counts down are less impressive than his pure stuff.

13. Brett Graves, RHP
Preseason rank: None (2014 Draft)
ETA: 2017
Scouting grades: Fastball: 60 | Slider: 50 | Changeup: 45 | Control: 55 | Overall: 45

Scouts loved Graves' athleticism and arm strength when he was coming out of high school in St. Louis in 2011, but his size contributed to him lasting until the Cardinals took him in the 26th round. He drew some interest from college football programs as a quarterback before deciding to focus on pitching at Missouri. Three years later, Graves signed for $510,000 as a third-rounder.

Graves has a quick arm that produces 92-94 mph fastballs that top out at 97 mph. He can throw the ball by hitters up in the strike zone, or he can induce groundouts in the lower part of the zone. Graves' hard slider shows some promise, while his changeup is a work in progress.

While Graves' size leads to questions about his durability, he helps his cause by filling the strike zone and keeping his pitch counts down. Graves maintains his velocity into the late innings, so he could become a No. 3 or 4 starter if he can refine his secondary pitches.

14. Daniel Gossett, RHP
Preseason rank: None (2014 Draft)
ETA: 2017
Scouting grades: Fastball: 50 | Slider: 55 | Changeup: 50 | Control: 50 | Overall: 45

Clemson has produced seven big league pitchers in the 2004-13 Drafts, and it could have an eighth on the way in Gossett. As a second-rounder this June, Gossett went higher than any of them, except for Pirates 2007 first-rounder Daniel Moskos.

Signed for $750,000, Gossett has a low-90s fastball that tops out at 94 mph. He commands the fastball well, which is crucial, because it's fairly straight. Gossett's best pitch is his hard slider, while his changeup is a reliable third offering.

Gossett doesn't have an imposing build, so scouts question if he'll have the durability to be a starter as a pro. If Gossett does shift to the bullpen, both his fastball and slider could play up and become above-average pitches as he works shorter stints.

15. Tucker Healy, RHP 
Preseason rank: None
ETA: 2014
Scouting grades: Fastball: 50 | Slider: 45 | Changeup: 40 | Control: 50 | Overall: 45

Healy went to Ithaca College, a Division III school in upstate New York, and he tied the school's saves record. The A's selected him in the 23rd round of the 2012 First-Year Player Draft, and they have put him on the fast track through the Minor Leagues.

Healy doesn't overpower hitters, but he has had no problem missing bats throughout his career. His fastball can get up to 95 mph, but it more often sits in the low 90s, with hard sinking action. Healy's slider has the potential to be a solid second offering. He throws from a low arm slot that adds to his deception, and that helps his stuff play up.

Healy aggressively attacks hitters, and he has shown he can be effective against both right-handers and left-handers. Having already pitched at three levels in 2014, Healy is on track to get a chance in Oakland's bullpen soon.  

16. Michael Ynoa, RHP  
Preseason rank: 11
ETA: 2016
Scouting grades: Fastball: 65 | Curveball: 55 | Changeup: 50 | Control: 40 | Overall: 45

The Athletics signed Ynoa to a then-international record $4.25 million bonus in 2008, only to watch him miss his first season with elbow tendinitis and his third season recovering from Tommy John surgery. In his first five pro seasons, he totaled just 115 1/3 innings, 75 2/3 of which came in 2013.

Ynoa still has the arm strength that made him rich. His fastball sits at 92-94 mph, and it reaches 97 mph. Ynoa's fastball is even harder to hit because he uses his 6-foot-7 frame to throw on a steep downhill plane. He hasn't had much time to refine his secondary pitches, showing more feel for his changeup than his hard curveball.

Ynoa's control and command are works in progress as well. In order to keep him healthy and expedite his development, Oakland will make him a full-time reliever going forward. He should add even more velocity in that role, and he could wind up as a closer if he adds some polish.

17. Billy Burns, OF
Preseason rank: 9
ETA: 2015
Scouting grades: Hit: 50 | Power: 20 | Run: 80 | Arm: 30 | Field: 55 | Overall: 45

Though Burns lasted 32 rounds in the 2011 Draft, the Nationals enticed him to sign for $75,000, and they got him to resume switch-hitting in pro ball after he had abandoned it at Mercer. Burns broke out in 2013 by ranking third in the Minors with 74 steals, and he ranked ninth with a .425 on-base percentage. Washington traded him to the A's in December for Jerry Blevins.

The son of former New York Jets running back Bob Burns, Billy has top-of-the-scale speed, and he focuses on maximizing it. He uses a patient and contact-oriented approach to get on base and create havoc. Burns has the potential to become Oakland's most dynamic basestealing threat since Rickey Henderson.

Burns' style leaves him with next to no power, and some scouts wonder if pitchers will be able to overwhelm him at the big league level. His speed allows him to cover lots of ground in center field, though he lacks some defensive polish. The Nats often deployed Burns in left field. Burns lacks arm strength, but he tries to make up for it by getting to balls quickly.

18. Ryon Healy, 3B/1B
Preseason rank: None
ETA: 2016
Scouting Grades: Hit: 50 | Power: 50 | Run: 35 | Arm: 45 | Field: 45 | Overall: 45

Though his lackluster .230/.255/.402 pro debut might have indicated otherwise, Healy was one of the best college bats available in the 2013 Draft. A third-rounder that June, he skipped a level to high Class A this year and he has done a better job of solving pro pitching.

Healy has a short and quick swing with loft, giving him the potential to hit for both average and power. Healy does a nice job of using the entire field, though his plate discipline has been surprisingly spotty since he turned pro. It's possible that Healy could develop into a .275 hitter with 18-20 homers per season, albeit with few walks.

Healy's bat will have to carry him. He has a fringy arm and below-average speed, making it a challenge for him to play third base. Oakland also has prospects Nunez and Chapman at the hot corner, and third base ultimately could be Robertson's best position. Healy likely will wind up at first base.

19. Aaron Shipman, OF
Preseason rank: None
ETA: 2017
Scouting Grades: Hit: 50 | Power: 20 | Run: 60 | Arm: 60 | Field: 55 | Overall: 45

The Athletics saw five-tool potential when they paid Shipman $500,000 to sign as a third-round pick out of a Georgia high school in 2010. His progress has been slowed by a series of injuries, and his power hasn't developed as hoped. But Shipman is still athletic, and he was enjoying his best season as a pro until he was sidelined by an oblique strain.

Shipman's speed and arm strength both grade out as better than average, though he's still refining his instincts to make the most of them on the basepaths and in the outfield. He has shown improvement as a basestealer, but he has seen most of his time the last two years in left field rather than center or right.

With Shipman's quickness and discerning eye at the plate, he could make for an intriguing leadoff hitter. However, he needs more aggressiveness and strength so he can drive balls more consistently. If Shipman can't cut it as a regular, he may find a big league role as a speedy fourth outfielder.

20. Jaycob Brugman, OF
Preseason rank: None
ETA: 2017
Scouting Grades: Hit: 50 | Power: 45 | Run: 50 | Arm: 60 | Field: 50 | Overall: 45

A 39th-round pick out of an Arizona high school in 2010, Brugman turned down the Yankees in order to attend Brigham Young. Oakland signed Brugman for $50,000 as a 17th-rounder last year, and he has gotten off to a better start in pro ball than most members of the Athletics' 2013 Draft class. While his arm is his only true plus tool, he doesn't have a glaring weakness.

Brugman couples a smooth left-handed swing with good patience at the plate. He has the power potential to hit 15 homers per season at his peak. Brugman is an average runner, though he's not a basestealing threat.

Since turning pro, Brugman has seen action at all three outfield spots. He has enough arm strength to play right field, but Oakland has deployed him mostly in left this season. It remains to be seen if Brugman can develop into an everyday player at the big league level, but his broad base of tools could make him a useful reserve.

Jim Callis is a reporter for MLB.com and writes a blog, Callis' Corner. Follow @jimcallisMLB on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.