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3/14/2014 10:09 P.M. ET

Melvin impressed by Leon's strong spring

SURPRISE, Ariz. -- Arnold Leon entered Spring Training with no shot of making the A's Opening Day roster.

But the 25-year-old Leon has made an impression and if he continues to pitch as he has, a chance to make to the 25-man roster could come sooner rather than later.

Leon, a native of Culiacan, Sinaloa, Mexico, has not given up a run in seven innings this spring. He has four strikeouts to one walk and opponents are hitting .118 against the right-hander.

"Leon has impressed. He'll be a guy that knocks on the door," A's manager Bob Melvin said this week.

Leon, in the wake of Jarrod Parker being scratched, will start Saturday's split-squad game against the Rangers at Phoenix Municipal Stadium.

In his fourth big league camp, it will be Leon's first Cactus League start.

Leon made just 12 professional starts before last season, when the A's converted him from a reliever and he made 24 starts between Double-A Midland and Triple-A Sacramento.

"I can do both. I know how to do both," said Leon, who likes the routine of a starter. "But that helped a lot. As a starter I can throw all my pitches."

Leon has four pitches and can use up to five, he said. Those have helped this spring, but moreso have been the lessons learned in past springs with the big league club.

"I'm more experienced. I know how things go in Spring Training," Leon said. "I know not to do too much with pressure, just have fun. I'm just trying to pitch like in the season."

Melvin took notice.

"We were looking at shorter stints with him last year," Melvin said. "We're lengthening him out a little bit now and he looks way more comfortable now. Just his demeanor on the mound, and you're seeing the results, too. This is a guy, as far as our pitching prospects go, is way up there."

O'Flaherty's Tommy John recovery on track

SURPRISE, Ariz. -- Eric O'Flaherty felt good after Tuesday's bullpen session, his first since undergoing Tommy John surgery in May, and is expected to throw another on Saturday.

"There are good days and bad days, but it's progressing as it should," O'Flaherty said. "We're right on track. On the bad days it hurts and on the good days I think I can pitch tomorrow. But the whole point is to stay steady and right on track."

O'Flaherty compiled a 1.98 ERA the last five seasons with the Braves. He signed a two-year deal with the A's in the offseason, with the team aware he would not be healthy until sometime in the middle of the season.

"There are days when the ball feels like a wiffle ball and days it feels like you're trying to throw a brick," O'Flaherty said. "You just take it day by day. The whole time we haven't had a deadline or a target date, just because that takes a lot of pressure off. It makes it a lot easier."

O'Flaherty said he doesn't have his own target date either.

"I just want to do it right. You hear 12 months and that's what you have in your head," he said. "But talking to the trainers here, that may not be best. They're not ruling it out, but let's shoot for 13 months or 14 months, something a little safer and see where I'm at."

Worth noting

• Outfielder Michael Taylor, who is out of options, hit his third home run of the spring and stole a base Friday against the Royals.

• Speedster Billy Burns had three hits but also committed a costly error in left field.

• Left-hander Sean Doolittle gave up three runs in two-thirds of an inning. He has allowed six combined in his last two appearances, both against the Royals.

• Minor Leaguer Daniel Robertson got the start at shortstop in Surprise, while Hiroyuki Nakajima remained in Minor League camp in Phoenix.

Craig Gentry (lower back strain) hit soft toss in the batting cage and Melvin said the utility outfielder should be close to taking batting practice on the field. As to whether he could be ready for Opening Day, it is still unclear.

• First baseman Daric Barton (hamstring) is expected to return to the field Saturday as part of the A's split-squad game at the Giants. Barton last played March 8.

Chris Gabel is a correspondent for MLB.com This story was not subject to the approval of Major League Baseball or its clubs.