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6/30/2013 4:48 P.M. ET

Parker to test sore hamstring with bullpen session

OAKLAND -- Whatever the A's have determined regarding the health of Jarrod Parker, who left his start Saturday with right hamstring tightness, no one appears too inclined to share.

"I got nothing," Parker said at his locker Sunday, stopping reporters from asking before they could even start.

A's manager Bob Melvin mirrored Parker, saying his right-hander had "some lingering soreness when he played catch" but that such side effects aren't necessarily indicative of something worrisome.

"That's to be expected," Melvin said. "Whether it's a cramp or a strain or whatever you want to call it, when you have that and you're doing a physical activity in the fashion he did, it's probably typical that there is some soreness today."

Melvin added that Parker's availability for his next start will be determined based on his bullpen session on Tuesday.

Parker had cruised through his first 3 2/3 innings in what was shaping up to be a pitchers' duel with Cardinals ace Adam Wainwright before the incident, which occurred following his 48th pitch of the game.

He entered Saturday's outing with a 4-0 record, 2.34 ERA and .176 opponents' batting average over his previous six starts after beginning the year 1-5 with a 7.34 ERA and a .345 opponents' batting average.

Weeks getting look in center field at Triple-A

OAKLAND -- Jemile Weeks received his first start in center field for Triple-A Sacramento on Saturday as the A's once highly touted prospect continues his quest to return to the Major Leagues.

Oakland's No. 1 pick in the 2008 First-Year Player Draft has bounced around the infield and struggled offensively in the minors, but a change of position could help provide versatility for the A's and manager Bob Melvin.

"Athletically, he could probably play anywhere in the outfield," Melvin said. "My understanding was he was all on board for it. It might even have been his idea. [Michael] Choice has been playing the corners here as of late so there was a fit for it because there was quite a logjam trying to get him consistent at-bats at second base with Grant Green too. So we'll see how it plays out. But athletically definitely he has the skill set to do that."

Weeks went 1-for-4 with two strikeouts Saturday in the leadoff spot for the River Cats. He's hitting .265 in 72 games this season with 21 RBIs, 50 walks and 51 strikeouts.

He took to Twitter the morning after his first start patrolling center, saying: "REALLY woke up like, "Did I just start in Centerfield last night?". I never seen my 1st start ever coming now.#wontbreakme (2b,ss,cf,next?)"

Melvin platooning Vogt, Norris at catcher

OAKLAND -- As the effects of John Jaso's left palm abrasion continue to linger, A's manager Bob Melvin will keep flipping between the two-man platoon of Stephen Vogt and Derek Norris, with Vogt returning to the lineup Sunday.

Melvin said before the series with the Cardinals started that there was a chance Jaso could be sidelined until Oakland's series against the Cubs, which starts Tuesday, so that Jaso won't have to join the disabled list.

"That's what we're hoping not to do," said Melvin, who has insisted that Jaso is available to pinch-hit if necessary. "That's why we're waiting as long as we have. Hopefully that's not the case. We haven't used him. We would be able to backdate it. But the reason we're going in the direction that we are right now is we're hoping he doesn't have to go on the DL."

Vogt's insertion to the starting lineup comes after receiving Saturday off so Norris could receive some much needed playing time, as he continues to try and work out a recent slump.

Norris responded to the opportunity by recording two of the five hits that Cardinals ace Adam Wainwright allowed in his complete-game win over the A's.

"I tried not to do too much, just tried to take what he gave me because he knows what he's doing on the mound," Norris said.

Engaging with that mindset has been a challenge for Norris, who entered Saturday's contest 4-for-39 over his previous 13 games.

"I made the mistake the last few weeks of trying to do too much when I get in there instead of just take my singles and waiting for a mistake to then do my damage," Norris said. "I've been trying to do my damage on pitches that aren't pitches I normally try and hit. I made a small adjustment yesterday to try and take a pitch I wanted to hit and not do too much with it."

When health isn't a concern, Melvin prefers inserting catchers based on matchups. And when opportunities decrease due to poor play, capitalizing on what can be infrequent at-bats becomes paramount.

"It's very tough, especially when you're not out there every day," Norris said. "You want to try and make a statement and you want to prove to the coaching staff and the front office that when you get in there you make a positive influence on the game, and when you don't, knowing that you have a few days, possibly, to think about what you could've done differently that day, sometimes it can wear on you.

"The only thing you can do is stay positive, and whenever our name is on the lineup card, contribute as much as we can."

Jeff Kirshman is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.