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9/6/2013 10:27 P.M. ET

Moss seeing more at-bats against lefties

OAKLAND -- Brandon Moss' recent production is forcing the A's to occasionally stray from their typically strict platoon system these days.

Moss made just his 10th start against a left-handed starter on Friday night, representing the only lefty in the starting lineup against Astros southpaw Dallas Keuchel.

"Our front office does a good job of monitoring and evaluating our lineup and when we'll have an extra lefty in the lineup," said manager Bob Melvin. "A lot of it has to do with how Brandon's swinging, and he is swinging awfully well. He's had some decent at-bats of lefties in-game too."

Moss hit home runs off a pair of Detroit's lefty relievers just last week, giving him a total of four on the season vs. southpaws in 70 at-bats. Overall, his batting average remains .200 against left-handers, compared to .261 against right-handers, but that doesn't reflect his recent success: He has a .308 clip vs. lefties since Aug. 1.

"I know that in my career, until this year, I hit lefties better than righties for average, but I don't have the power against them like I do against righties just because everything's away," Moss said. "Everything goes away, and it's just a little bit tougher to hit that for power."

Still, does Melvin see Moss, who is batting .333 with eight home runs in his last 17 games, potentially stepping into an everyday role at some point in his career, rather than one defined by a platoon?

"I do," he said. "But the team is set up a certain way. We do play the percentages on a particular day, so there will be some left-handers we pinch-hit against and others that we'll leave him in for. He's having a terrific season for us, and he's a big part of the offense when we're going good."

"I don't put anything past myself, but I don't want to get too far ahead, either," Moss said. "I try to focus on whatever my role is and make the most of that. If I'm in there, like tonight against a lefty, I'll do the best I can. There's a lot of tough righties that are just as tough as some lefties, so you just got to battle."

Jaso 'helpless' in recovery from concussion

OAKLAND -- The A's have three healthy and capable catchers on their roster, sometimes making it easy to forget there's a fourth who's wanting to join the party.

It's been 44 days since John Jaso -- recovering from a concussion -- last played in a game, and time's running out for him to appear in another before season's end.

"I'm wondering that," Jaso said Friday. "We'll just have to see how it goes. I can't control anything. All I can do is lie about it or tell the truth, and I'm just telling the truth and letting the professionals decide."

The professionals, notably leading concussion authority Dr. Michael Collins, told Jaso to cut back on baseball activity this week, after he began having symptoms -- like dry heaving -- again while doing batting cage work. So he's limited to stationary workouts for the time being, no closer to joining the team for on-field work and batting practice than he was weeks ago.

The A's have played 39 games since Jaso was placed on the disabled list. The lengthy recovery time is substantial, but often too typical. Red Sox catcher David Ross recently returned to Boston's roster after missing 54 games with a concussion.

"Everyday life is pretty simple," said Jaso, who was the A's starting catcher on Opening Day, "but as soon as I start doing up-and-down movements, stuff outside, even just the jolt your body gets from swinging the bat, it messes me up.

"I've had concussions before and it hasn't taken this long. I'm not the first guy this has happened to, though, and I understand that. Still, it's such a helpless feeling and you don't really want it. You just come to a point you realize it is what it is."

Jaso, who said he wakes up to buzzing in his ear each morning, was batting .271 with a team-leading .387 on-base percentage following his last game in Houston on July 24. His ability to get on base -- he had an OBP of .415 in his last 16 games -- has been missed on a team that often struggles without the long ball.

"Not being able to contribute, it's the worst," Jaso said. "But worrying doesn't do anything for you. That's the way I live my life."

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.