OAK@CLE: Nakajima sustains hamstring strain injury

SAN FRANCISCO -- While it's not yet known whether shortstop Hiro Nakajima will require a trip to the disabled list for his left hamstring strain, the A's are at least certain he won't play in this weekend's three-game exhibition series against the Giants.

The A's ventured across the Bay Bridge for the first game of the series on Thursday, and it was during that time that Nakajima was scheduled to be seen by the team's doctors to determine the next course of action.

Doctors confirmed the strain but offered no indication of how much time he'll miss, making a DL stint all the more likely.

Uncertainty not only surrounds Nakajima's health, but his ability to compete in the big leagues. The Japanese shortstop struggled all spring, both on defense and at the plate, and his slow progression has cleared the way for Jed Lowrie to take over everyday shortstop duties.

The A's aren't yet ready to say as much, but there's no denying that his injury only adds to an already difficult adjustment period. For now, though, they're not ruling him out of playing in the first week of regular-season games.

"It's tough to say, it is," A's manager Bob Melvin said. "If he misses three games here and a couple back there, it would be difficult to get back into the swing of things, but I'm not really sure yet."

Jaso catches another learning curve

Outlook: Jaso will platoon against lefties in '13

SAN FRANCISCO -- Learning a new pitching staff is simply becoming another rite of Spring Training for John Jaso.

The new A's catcher is in the process of learning his third different pitching staff in as many years, and with four days to go before Opening Night, he feels he's as ready for regular-season action as he'll ever be.

"It's definitely a process, but they've made it easy on me here," Jaso said Thursday. "It's a pretty easy staff to catch, and they're good personalities, so you can talk to them pretty easily if you have suggestions. They're going to listen, and they're going to give me some input, too.

"There's a lot of work that goes into it, but I feel like we've made a lot of progress."

Jaso was chasing plenty of pitches in the dirt during the early going in camp, as he became acquainted with the movement and spin on each hurler's pitches. Finesse pitcher Tommy Milone naturally proved the easiest to catch, Jaso said, while Ryan Cook's two-seamer made him the hardest.

He's found his stride with everyone in between, and the A's are more than confident with his game-calling abilities heading into the season, especially considering his resume. Jaso has already worked with a pair of superb pitching staffs, having caught a 2011 Rays team that compiled a 3.58 ERA and a 2012 Mariners squad that posted a 3.76 ERA.

Now, he's prepared to play catch with a rotation that includes Brett Anderson, Jarrod Parker and Milone.

"At this level, what you do behind the plate is the thing that's most criticized about you," Jaso said. "Coming up through the Minors, it's hitting that's allowed people to jump up level to level. Here, it's all about catching, and going from team to team to team, it's definitely had to become my priority next to hitting.

"Learning a new pitching staff was obviously something I had done before, and I had confidence in doing it. It's a fun challenge, as well."

Said manager Bob Melvin: "First it takes a little while to learn the pitching and subtle movements on guys. There were some balls getting by him early in camp that aren't getting by him now, and I think each and every time he catches a guy he's that much more aware and knows what to expect. I think he's starting to acclimate and get better and better."

The left-handed hitting Jaso is likely to get the start against former teammate Felix Hernandez come Opening Night on Monday. Beyond that, it's not yet clear how Melvin will split playing time between Jaso and Derek Norris, though a platoon may make the most sense. Jaso has no time, or care really, to worry about any of that.

"I don't know what's going to happen with our situation," Jaso said. "I'm just happy someone wanted me on their team. Last year with the Mariners, we were carrying three catchers, and I sat on the bench for almost a month and didn't see any playing time. I was just happy to be there. I didn't feel like complaining or that I was mad at anyone. I feel like I worked too hard in the Minor Leagues and spent too much time there to be mad."

Bullpen spots still up for grabs

Outlook: Blackley is more effective in the bullpen

SAN FRANCISCO -- The A's have 12 relievers on their roster and just three more days to narrow that field to seven.

"That's a good problem to have, yet there will probably be a few guys that deserve to make the team that don't," manager Bob Melvin said. "There's usually a couple of guys every year where that's the case, but probably a few more this year, based on the depth that we do have in the bullpen. The last few cuts will be difficult."

But perhaps the actual decisions won't be. Closer Grant Balfour and his set-up men, Ryan Cook and Sean Doolittle, are locks to make the team. That leaves four open spots, and there just so happens to be four relievers -- good ones -- who are out of options.

That group includes lefties Jerry Blevins and Travis Blackley and right-handers Chris Resop and Pat Neshek. Blevins' spot is seemingly secure, and Resop and Neshek don't have much to worry about, either, especially after producing zero ERAs this spring. Blackley, meanwhile, has a 14.21 mark, though his contributions to the 2012 club may end up outweighing those struggles when it comes down to decision time.

"Options always come into play," Melvin admitted. "That doesn't mean that that's the way it's going to go, but certainly when you do have depth and you try to keep everyone in the fold, that sometimes happens. Whether that's the case here, I'm not sure yet."

Blackley is perhaps the most versatile of any pitcher on the A's roster, having pitched effectively as both a starter and reliever for the team last year. Should he make the team, he'd be mostly used in a long-relief role. Melvin said Thursday that he's not committed to carrying a long reliever, but hinted that the job could be done by several others in the event Blackley is not on the team. He dropped the names of Pedro Figueroa, Jordan Norberto, Evan Scribner and non-roster invitee Mike Ekstrom, who, like Hideki Okajima, could all be the odd men out.

Of Blackley, Melvin said: "He hasn't pitched as well as he'd like to this spring, but he did do some very good things for us last year, whether it was starting or long relief, so that plays into it.

"We have a pretty good idea [ultimately], other than maybe one spot," Melvin said. "Maybe two, but maybe closer to one. One and a half. Let's leave it at that. It could come down to some performances these last three days."

Rodriguez undergoes Tommy John surgery

MLB.com's Jane Lee on A's acquiring Lowrie, Rodriguez

SAN FRANCISCO -- The A's announced that reliever Fernando Rodriguez underwent successful Tommy John surgery this week.

The right-hander's procedure was performed by Astros' team physician Dr. Thomas Mehlhoff at the Texas Orthopedic Hospital in Houston on Wednesday. "[The surgery] had no complications and Rodriguez will be rejoining the A's on Saturday to begin his rehabilitation process," the team said in a release.

The 28-year-old Rodriguez, acquired by the A's along with Jed Lowrie from Houston last month, is facing at least a year's worth of rehab time on his elbow.

"Everything went really well, so he should feel good about that," manager Bob Melvin said. "He still has quite the career ahead of him. This is just a year setback. It's disappointing, but especially for a power pitcher like him, now you don't have to worry about that anymore.

"Really, after Tommy John, with the technology, guys come back throwing harder. Having that secure feeling that that thing is triple-wrapped in there, you don't have to worry about that type of injury again, knock on wood."

Rodriguez compiled a 10.13 ERA in four Spring Training games with the A's before learning that his ulnar collateral ligament was torn. He was placed on the 60-day disabled list last Saturday.

Worth noting

• Melvin said the lineup he trotted out for Thursday's game against Giants right-hander Tim Lincecum could "potentially" be the same one he writes out for Monday's Opening Night contest vs. Seattle's Felix Hernandez.

If so, it will read like this (the inclusion of a designated hitter, not used Thursday, is reflected): Coco Crisp CF, Lowrie SS, Josh Reddick RF, Yoenis Cespedes LF, Brandon Moss 1B, Seth Smith DH, Josh Donaldson 3B, Jaso C, Eric Sogard 2B.

• Cespedes' home run Thursday was his fifth in his last nine games.

"That's what he does, drives in runs," Melvin said."Not a surprise."

• Minor Leaguers Scott Moore and Conner Crumbliss are with the A's in the Bay Area for the three-game set against the Giants. The versatile players give Melvin extra options in the late innings while the club partakes in National League-style play in San Francisco.