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7/31/2013 4:16 P.M. ET

Jaso unlikely to return from DL this weekend

OAKLAND -- A's catcher John Jaso, who's on the seven-day concussion disabled list, said he was feeling better on Wednesday morning but remained doubtful he'll be able to return when eligible Thursday.

The A's have an off-day Thursday, but a return Friday or this weekend seems unlikely for Jaso since he hasn't resumed any baseball activity.

Jaso was scheduled to undergo a series of tests with the team's trainers on Wednesday and was looking forward to getting answers on what's next.

He's still experiencing some concussion symptoms, including buzzing in his ear each time he wakes up -- something he never experienced with his first two concussions, suffered in 2005 and '10.

"I'll talk to the trainers today and find out some stuff," Jaso said. "I want to play, but I know we have to be careful. If you put a catcher back out there, how often do you get hit in the face mask? The probability is high that the same thing could occur out there again."

In the meantime, the A's will rely on Stephen Vogt to share platoon duties with Derek Norris behind the plate. Entering Wednesday, Oakland was 8-0 in games started by Vogt at catcher.

Callaspo to see time at second base with A's

OAKLAND -- How long has it been since Alberto Callaspo last took grounders at second base?

"A long time," Callaspo said, smiling.

Oakland's new infielder, acquired from the Angels for Minor Leaguer Grant Green on Tuesday night, hasn't played there since 2010. He hasn't been a regular there since 2009. But his new manager, who just so happens to be the first manager he ever had in the big leagues in Arizona, isn't concerned about this.

"Because that's his natural position, that's where he started out," Bob Melvin said. "Now there is some uncertainty, obviously, because he hasn't played there a couple years, but he's always been a sure-handed defender. My talk with him this morning was that it doesn't matter where we play him."

Callaspo, 30, will mostly platoon with Eric Sogard at the position, though he can also spell Josh Donaldson at third base, too. No matter, he's happy to be joining a first-place club.

"I was surprised," he said, just minutes after walking into the clubhouse, fresh off a flight from Texas. "They took me out in the sixth inning last night and I was thinking, 'What happened?' Now I'm here and I'm trying to keep doing my job, playing 100 percent and help this team."

"He's excited about being here," Melvin said. "First day with your new club, flying in the morning, meeting everyone, it can kind of be a whirlwind. We're happy about having him, and it's probably a good thing we have an off-day tomorrow so he can get acclimated a little bit."

Callaspo remained on the bench on his first day in Oakland, with Sogard drawing the start against Toronto knuckleballer R.A. Dickey, but he got a crash course at second base prior to the game, fielding grounders from infield coach Mike Gallego.

It's Callaspo's ability to get on base, though, that really sold the A's, who are on the hunt for a second consecutive American League West title.

"Switch-hitter, good from both sides of the plate," Melvin said. "I think one of the most difficult guys to strike out. You can hit and run with him. There are a lot of things you can do with him. So it is an upgrade for us. We feel good about having him here. We feel like he's a piece that fits real well for us."

"I'm just going to try to do something, try to help the team," Callaspo said. "If there's something they need from me, I'm going to try and do it."

With Callaspo on board, the A's opted to designate Adam Rosales for assignment. He was hitting just .193 in 50 games while serving in the same role Callaspo will now fulfill.

Oakland has 10 days to trade, release or pass Rosales through waivers, the same thing that happened to him a few weeks ago when he was initially designated to make room for Green.

"We still feel like he might be our best defender at shortstop in the organization," Melvin said. "It'd be nice to be able to keep him. We'll see if that's the case."

Reddick out of lineup day after taking knee to head

OAKLAND -- Josh Reddick was held out of the A's lineup for Wednesday's series finale against the Blue Jays after taking a knee to the right side of his head in a three-player collision the night before.

"He came in today with a little bit of a headache, and that's why I scratched him," manager Bob Melvin said. "We don't feel it's concussion symptoms, but anytime someone comes in with a headache after being hit on the head, you want to be careful with that."

Reddick's name initially appeared in the starting lineup, but after undergoing a series of tests, the A's chose to go with Chris Young in right field, ensuring Reddick not only one day of rest but two, thanks to Thursday's off-day.

"Hopefully, with both those days," Melvin said, "he'll be good to go Friday."

Reddick was going after a shallow fly ball in right field on Tuesday night. First baseman Nate Freiman and second baseman Jed Lowrie had the same idea, and Lowrie's knee rammed into Reddick's head as the ball dropped. Reddick remained on the ground for some time, but after speaking with Melvin and a team trainer, stayed in the game.

Worth noting

• Lefty Brett Anderson (right foot) will throw live batting practice on Friday, marking the first time he'll face hitters since beginning his rehab. Should all go well, Anderson believes the next step would be a rehab assignment.

• Beginning Thursday, the A's will enjoy three off-days in an eight-day span. Still, their rotation won't be altered.

"I really think, at this point in time, guys need some rest at this point of the year," Melvin said. "Guys seem to do well with an extra day or two."

Jane Lee is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.