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08/23/12 7:10 PM ET

Melvin confident Pennington will adjust to second

ST. PETERSBURG -- As Jemile Weeks prepares to find consistency in his swing with Triple-A Sacramento, Cliff Pennington is finding comfort with his new position -- Weeks' position.

Having shifted to second base upon the arrival of shortstop Stephen Drew, Pennington made his second straight start there on Thursday, this time at Tropicana Field for the first of a three-game set with the Rays.

Before Wednesday, Pennington had made each of his previous 439 starts at shortstop, a job he lost in the middle of his offensive struggles. Entering Thursday he was batting .199 with just 18 RBIs. It was just last year he tallied a career-high 58 RBIs to go along with a .264 average.

But manager Bob Melvin is confident in the infielder's ability to adjust to his new home.

"Based on the amount of shifts we have, he's over there working on double plays sometimes, anyway, during the course of the season," Melvin said. "It's not going to be a problem for him. It's just the different angles he has to deal with and getting used to those. But he's a good athlete and plays the middle of the diamond, so ... we feel like the learning curve will be shorter than longer for him."

Inge begins rehab assignment in Triple-A

ST. PETERSBURG -- Third baseman Brandon Inge, nursing a strained right shoulder, is slated to begin a rehab assignment with Triple-A Sacramento on Thursday, and is expected to make at least three starts for the River Cats.

Whether he'll make an immediate return to the A's afterward is unknown, but his temporary replacement figures to factor into the decision.

And why shouldn't he? Josh Donaldson, called up on Aug. 14 when Inge was placed on the disabled list, has provided plenty of production, batting .429 with a home run, five doubles and six RBIs over nine games. He's hit safely in each of the last six for the longest hitting streak of his career.

Those numbers have greatly enhanced the bottom third of Oakland's lineup. And although they trump the .224 average and .285 on-base percentage Inge compiled in 73 games, the elder Inge provides a veteran presence that could be integral down the stretch.

Playing time at third base, then, could be shared upon Inge's return.

"I think, based on what we've done all year, we're going to wait and see and make sure he's healthy and see what our best options are," manager Bob Melvin said. "I think everything kind of factors in, but we want to make sure he's healthy. This is an injury that, if this thing keeps slipping out, it could be a surgical type of thing. We want to make sure that he's throwing the ball from a few different angles and so forth. He'll get at least three games there to start, and then we'll see where we are."

It wouldn't be the first platoon the A's have used this season -- not even the second or third, in fact. Oakland has, at one point or another this season, used a platoon at every infield position. Still, there have been more wins than losses.

"I can't remember the last time there's been this much turnover and this much platooning or changing in positions and so forth with the type of success we've had," Melvin said. "I think that the front office is very good at targeting guys when they're playing well, matching up, all of the above. Not only have we embraced it as a coaching staff, but ... so have the players, and they understand we're trying to run our best lineup out there on a particular day, series, week or whatever."

Worth noting

• Right-hander A.J. Griffin (shoulder) made his first rehab start with Triple-A Sacramento on Wednesday, giving up three runs on four hits, with three walks and four strikeouts in just 2 1/3 innings. Griffin threw 60 pitches, 34 for strikes.

"[It was] fair, which is fairly typical for your first time out," manager Bob Melvin said. "We feel like [he] doesn't need a whole lot of work, a command guy, but we'll see where we go from here with him."

Griffin is expected to make at least one more rehab start with the River Cats before possibly rejoining the A's; the roster will expand by the time he's ready.

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.