PHOENIX -- The A's first-base competition will surely heat up with the commencement of Friday's Cactus League opener, but contender Daric Barton will be limited to designated-hitter duties for now, as expected.

Barton, on the mend from right-shoulder surgery, recently had a cortisone shot and was instructed to take three days off. He should be swinging a bat again by Saturday, and could make his spring debut at DH in one of Monday's split-squad contests, manager Bob Melvin said.

Barton, 26, isn't expected to begin throwing again until mid-March, at which point he would only have a limited number of days to see game action at first base before the club departs for Japan. Such a timeline seemingly puts him behind competitors Brandon Allen, Kila Ka'aihue and Chris Carter. But that's not necessarily the case, given the club's familiarity with his defensive skills.

"We know what we expect of him, and we need to get him healthy before we can see some of those results," Melvin said.

Barton was the A's Opening Day starter at first base last year, but never got on track offensively -- hitting .212 with no home runs and a .267 slugging percentage in 67 games, before being optioned to Triple-A Sacramento in June. What he can do with the bat over the next few weeks will likely dictate his chances of starting the year in Oakland.

"I'd like to see everything," Melvin said, "but that's the thing that's going to come first. We feel good about his defense."

Cook's heat breaks a couple of bats

PHOENIX -- The A's are still educating themselves on right-handed reliever Ryan Cook, but they learned yet another thing about the pitcher in Thursday's intrasquad game.

His fastball can break a bat -- or two -- as he did in his 1-2-3 inning of work.

"We always thought he was a guy that had an exploding fastball with good movement and a little deception, blows up the bat right away and has a real quick inning," manager Bob Melvin said. "One knock on him is, maybe, his walks. But it looked like he was out there going right after guys."

It's hard not to glare at the eight walks he issued in 7 2/3 innings with Arizona last year, but Cook insists that stretch wasn't reflective of his typical performances. The 24-year-old righty, acquired in the Trevor Cahill trade, says he was simply "in a little bit of a funk at that point."

"Honestly, I've not struggled with a walk problem at all until then," said Cook, who also fanned seven in that time. "I was just a hair off here and there with my mechanics."

So Cook teamed up with D-backs pitching coach Charles Nagy and worked on being smooth to the plate, rather than speedy, and in doing so found a better sense of command during his second and final stint as a September callup.

"I realized I didn't need to change anything, just be smooth," Cook said. "So I'm trying to stick with what I do and hopefully raise the right eyebrows here."

Cook has a good chance of pitching his way into a bullpen that also includes the likes of Brian Fuentes, Grant Balfour, Joey Devine and Fautino De Los Santos. It was just this time last year when he was stripped of starter duties and made the transition to a relief role at the Double-A level.

Not four months had passed since the start of the regular season when Cook got the call to the big leagues.

"It was surprising and amazing," he said. "The walks, I think the move to the bullpen influenced that a bit. As a starter, I moved nice and easy, and wasn't worried about velocity or being nasty, if you will. There was much more adrenaline. But I'm going best when my fastball is lively and I can command it. The bad days are when I can't."

The A's have yet to see one of those.

"He's been real impressive," Melvin said. "He's definitely in the mix for a bullpen spot."

Donaldson shakes off error, has big day

PHOENIX -- It took three innings for a ball to make its way over to Josh Donaldson in Thursday's intrasquad game, and when it did, the result wasn't so favorable.

Donaldson, looking to grab hold of the third-base job vacated by the injured Scott Sizemore, misplayed a ground ball on a play that would have been deemed an error had it occurred in an actual game.

"By the time it got to me, I wasn't in a very good position to make the play," Donaldson said.

Such a miscue could shake up a young player, but it had the opposite effect on Donaldson. He quickly transformed from goat to hero -- not only by making a pair of impressive plays at third, but also hitting a go-ahead, three-run homer to right-center field that led to a 4-1 victory for the "home" team.

"I learned early in my career to take one play at a time," Donaldson said. "If I mess up, I'm not going to help the team by continuing to dwell on that. If I mess up, which is going to happen a few times this year, they're going to have to count on me to make the next play."

"I like the fact that he recovers," manager Bob Melvin said. "All of a sudden, he's thinking of what probably isn't a good play, and then he recovers and makes a great play the next time and then hits the ball about as far to right-center field as I've seen hit here. It ended up being a really nice day for him and, hopefully, confidence-wise, he feels that much better going into games [on Friday].

"I've heard from the developmental staff he's a guy that comes up big, and makes big plays and so forth."

Donaldson will receive plenty of looks on defense, but the A's are just as intrigued by what his bat can do -- especially after an offseason in which he learned valuable lessons by playing winter ball in the Dominican Republic.

"I've really worked hard this offseason to try to get back to my approach when I was younger, of just trying to make solid contact," Donaldson said. "I've hit for higher averages in my career, not so much the last two years. I've really focused on trying to drive balls. I'm trying to get back to just being more of a hitter than a power guy. And I feel if I make solid contact very consistently, my power numbers are going to be there."

Worth noting

• Baseball sources confirmed that Cuban outfielder Yoenis Cespedes is expected to be at Phoenix Municipal Stadium on Saturday to undergo a physical. His four-year, $36 million deal will be made official soon after, and it's likely Cespedes will finally join the team on Sunday. He will wear No. 52.

• Lefty Sean Doolittle, who has made the full-time transition from position player to pitcher, was one of eight hurlers to pitch in Thursday's intrasquad game. Doolittle faced four batters, giving up a triple and an unearned run.

"I thought he threw well," Melvin said. "He doesn't really look like a convert. He looks like a pitcher out there."