© 2013 MLB Advanced Media, L.P. All rights reserved.

7/24/2013 7:19 P.M. ET

Anderson throws 40 pain-free pitches in 'pen session

HOUSTON -- Mid-August is looking more and more like the time the A's can expect to welcome back lefty Brett Anderson, who continues to progress in his rehab without any issues.

Anderson, nursing a stress fracture in his right foot back to health, threw his second bullpen session of the week on Wednesday, tossing 40 pitches pain-free.

"He feels as good about this one as he did about the last one, maybe even better," manager Bob Melvin said. "I wasn't out there for this one, but he came in with a smile on his face and said he was nastier this time than he was last time."

The plan is for Anderson to throw another bullpen session before week's end. Should all go well, it's likely he'll then throw to hitters, possibly in a simulated game or simply live batting practice, before the A's decide if he's ready for a rehab assignment.

"Just depends if everything goes well," Melvin said. "We want to make sure every step that we take with him goes accordingly."

Jaso examined for concussion symptoms

HOUSTON -- A's catcher John Jaso has taken a foul ball to his face mask twice in as many days, leading to doctor visits on both occasions to check for concussion symptoms.

Following Wednesday's 4-3 win in Houston, which he departed after seven innings, Jaso underwent a series of vision tests, which came back normal. However, he still felt dizzy, making his availability for upcoming games uncertain.

Jaso, at least, should be able to rest Thursday, with a lefty in C.J. Wilson throwing for the Angels and Derek Norris likely drawing the start at catcher.

"My brain might like the rest, but at the same time I want to play," Jaso said before boarding the team charter. "I feel good right now. I feel like I'm working really good at-bats, so it's definitely not a time I'd want to rest or whatever. A lot of it will have to do with the trainer and what he feels is best."

Jaso went 2-for-3 with a home run, a double and a walk on Wednesday, before a foul ball drilled his mask in the seventh. On Tuesday, the same happened in the sixth.

"He was cleared and good for the game, and once he took another one, he told me he had a little headache and that was it," manager Bob Melvin said. "You can't chance that."

Jaso is very familiar with concussion tests, having undergone them in the Minors when he was diagnosed with one.

"It's definitely nothing new to me, it just gets a little scary sometimes," he said. "Like yesterday after I got hit, I was kind of fearing the pitch he was going to throw after that. I had to call time, because I didn't know whether I was going to see the pitch or not. I don't want to hurt the team at the same time. I know, blocking balls, I want to be on top of that in one-run ballgames. I don't want to let pride get in the way of that.

"We're going to have to see how things go. I've got some head problems right now. I don't like making a habit of this."

A's recall infielder Rosales to boost defense

HOUSTON -- More than anything, manager Bob Melvin said, calling up infielder Adam Rosales on Wednesday was about "getting back to the symmetry we had before."

Rosales, designated for assignment on July 8 amid offensive struggles, isn't back because those issues are no more. He hit just .240 over six games with Triple-A Sacramento following his outright, but it's his defense the A's were yearning to have again.

Oakland has committed seven errors in five games since the break, including six in its last two contests, and Grant Green, optioned following Tuesday's loss, didn't look sharp in his five starts at second base. He was charged with three errors in that span.

Green, the A's top pick in the 2009 Draft, was also hitless in 15 at-bats to start his big league career.

"Any time a guy like Grant Green, one of our top prospects, gets to the big leagues and gets a taste of it, it's a good thing, regardless of the results," Melvin said. "I told him that last night. His at-bats were good in the last game. For a younger player to come up that's used to playing every day and have to acclimate to not playing every day can be difficult, but you have to learn to acclimate to it if that's your role, and he'll be better for it the next time he's here."

Rosales was hitting .200 with four home runs and eight RBIs in 48 games with the A's when he was designated. His role -- playing shortstop, with Jed Lowrie at second base, against left-handers -- figures to be the same.

"He's a plus defender at every position," Melvin said. "We have been having some defensive issues here recently, and he's one of the guys that can clean that up."

To make room on the 40-man roster for Rosales, the A's designated infielder Vinnie Catricala, who was playing at the Double-A level, for assignment.

Worth noting

• Coco Crisp entered Wednesday having compiled four hits in his last 12 at-bats, after tallying just 15 in his previous 90 at-bats (.167).

"When we're playing our best baseball," Melvin said, "he's playing his best baseball. I don't want to put that kind of pressure on one guy, but he's the engine that gets us going."

• The A's loss on Tuesday night was their first when leading after eight innings since Aug. 4, 2012. Oakland is 49-1 when leading after eight frames this season, as well as 44-2 when leading after seven.

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.