© 2014 MLB Advanced Media, L.P. All rights reserved.

3/25/2014 8:48 P.M. ET

Callaspo to learn as he goes in platoon at first

PHOENIX -- Alberto Callaspo will be the A's first baseman on days the club faces a left-handed starter this season. Manager Bob Melvin confirmed as much Tuesday morning and said he felt confident putting the versatile infielder out there, despite his limited experience at the position.

"He's done some hard work and drills out there," said Melvin, who first mentioned the possibility of such a scenario in the offseason.

This means Brandon Moss and Daric Barton will share time at first base against right-handed starters, though Moss will most likely draw several starts at designated hitter -- at least in the early going. Moss has proved to be a reliable defender at first base, but Barton is still considered better with the glove.

"We're going to play each and every game what we think the best matchup is," Melvin said. "There's different factors -- who's swinging well, and if we have chinks in the armor as far as injuries and so forth. But with us, there's really no set lineup, and that dynamic [at first base] would suggest that, too."

Callaspo had never played first base before this spring, and it remains a work in progress for the 30-year-old, who will also continue to provide a backup option at second and third base.

Callaspo is a career .300 hitter against lefties, reaching base against them at a .346 rate.

Parker has successful Tommy John surgery

PHOENIX -- A's right-hander Jarrod Parker had successful Tommy John surgery in Pensacola, Fla., on Monday.

It was the second such surgery performed by Dr. James Andrews on Parker, who is looking at a rehab spanning at least 16 months the second time around.

"Everything went well," said manager Bob Melvin, who had yet to speak with the pitcher.

Parker has tweeted twice since the procedure, on Monday telling his followers, "All good! #BeenThereDoneThat lets go Athletics" and on Tuesday, sharing, "Appreciate & want to thank everyone for the support, nice messages and kind words! Finished 1st follow up/therapy."

Parker, 25, was on the heels of a strong 2013 season (12-8, 3.97 ERA) and in line for his first career Opening Day start before learning he had again torn the ulnar collateral ligament in his elbow. He first had the procedure in 2009.

Norris shows potential beyond platoon role

PHOENIX -- Derek Norris is a force to be reckoned with these days, thanks to a new plate approach that has him consistently squaring up the ball.

The A's catcher collected three more hits Tuesday and is batting a team-leading .436 with 12 RBIs in 39 spring at-bats -- many of them against right-handers. But when the season begins, Norris is expected to resume the same platoon role he served last year, meaning John Jaso will start most games vs. righties.

"Certainly there are stretches where you have a lot of righties where it's difficult to have him sit that long, whether it's a day game after a night game," manager Bob Melvin said. "I want to keep him current, but we'll see."

"I'm a firm believer in, if you keep performing and you play to the best of your ability, you're going to force their hand more and more," Norris said. "In the past I've had my fair share of ups and downs -- more downs, but hopefully it's a step in the right direction, and hopefully I can carry this on into the season.

"I'm just continuing things that I fixed last year, most importantly trying to stay balanced and making sure I have my timing going into the season."

Norris has incorporated a leg kick in his stance, having previously struggled to be consistent with his timing because he was too heavy on his front side.

"It kind of counteracts the hands going back," he said. "It helped keep me a little more balanced and a little lighter on my front side, which allows me to slow the game down a little bit and see the ball. The biggest thing for me is not being afraid to get beat. My whole life I've tried to yank stuff on the outer half, trying to pull it to left, and I've reached a mental adjustment to kind of let the ball travel, and not being scared to get jammed is the biggest thing."

"He's had one of the more impressive springs, and we don't look too much at Spring Training numbers, but you can't help but notice the adjustments he's made," Melvin said. "He's got a very consistent approach. He's not trying to do too much as far as pulling the ball. It looks like his swing is shorter, and it might not be, but the way he has his hands now, it looks that way, and he works on it every day. He has a very good understanding now of what his mechanics are.

"He's getting just as good swings off righties as he is off of lefties."

Norris' splits were dramatic last year. He hit .320/.410/.580 in 150 at-bats against left-handers, compared with .149/.261/.184 in 114 at-bats with right-handers on the mound.

"I didn't see them much last year, and when I did, it had been weeks, and that makes it a little more difficult," he said. "I'm not making excuses for myself, but it's definitely nice to see them regularly and to get a rhythm and see both sides."

Punto most likely out until Bay Bridge Series

PHOENIX -- The A's plan to keep infielder Nick Punto out of game action for at least two days, after the veteran experienced left hamstring tightness in Monday's contest.

Punto played just two innings in the field against the Rangers before he was pulled as a precautionary measure.

"He's fine," manager Bob Melvin said. "It'll probably be two days, which is fine. He was off today, anyway, and tomorrow will be a limited day for everyone -- probably one at-bat -- so if he's going to miss a couple days, those are two good days to miss."

Melvin expects Punto to be able to play in the three-game Bay Bridge Series, spanning Thursday to Saturday in advance of Opening Day. Once the season begins, the plan is for Punto to form a platoon with Eric Sogard at second base and also to back up Jed Lowrie at shortstop.

Worth noting

Craig Gentry went 2-for-6 in a Minor League game on Tuesday, and Ryan Cook and Fernando Rodriguez both pitched an inning in the same game without any issues.

Dan Straily and Tommy Milone will form a tandem starting duo for Saturday's exhibition games against the Giants in Oakland.

Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.