SAN FRANCISCO -- A's manager Bob Melvin was ejected for the second time in three days Saturday, after engaging in a pair of arguments with home-plate umpire James Hoye stemming from a hit-by-pitch call awarded to Giants pitcher Ryan Vogelsong in the seventh inning of a 4-0 A's loss.

With a runner on first base and no outs in the bottom of the frame, Vogelsong gestured to bunt against right-hander Tyson Ross, whose pitch to the opposing hurler appeared to hit his bat, but instead was ruled a hit-by-pitch.

Melvin came out to question the call, before retiring back to the dugout, at which point reliever Grant Balfour was brought in and allowed his two inherited runners to score, along with two more. Upon Balfour's departure with two outs, Melvin again exchanged words with Hoye and was quickly tossed.

"I just thought it hit the bat," Melvin said. "It sounded like it hit the bat."

He wasn't too pleased, however, with his decision to come out a second time and restart the feud.

"I shouldn't have done that," he said.

On Thursday, Melvin was ejected by home-plate umpire Laz Diaz in Texas after Elvis Andrus' popup bunt was incorrectly deemed a trap when replays showed A's pitcher Brandon McCarthy caught it. Diaz later called Melvin to acknowledge he made the wrong call, but when asked if he expected as much from Hoye, the skipper replied, "No."

Anderson's rehab hits minor speed bump

SAN FRANCISCO -- Lefty Brett Anderson has encountered his first speed bump on the road back from Tommy John surgery, as he's been shut down with forearm stiffness commonly associated with the procedure.

The setback is not of great concern, manager Bob Melvin assured, especially considering Anderson is ahead of schedule in his rehab.

"He's going to slow down for a few days here," Melvin said. "It's rare you have no speed bumps in this process, and to this point it's been miraculous he's had nothing."

Anderson, who is in Arizona, most recently pitched one inning in a simulated game, using all of his pitches. He's expected to return to the A's rotation shortly after the All-Star break.

Barton working to be more aggressive at plate

SAN FRANCISCO -- Less shy, more aggressive.

That's the plate approach the A's are trying to preach to the normally patient Daric Barton, and it appears the work with hitting coach Chili Davis is paying off. Barton entered Saturday batting .556 (5-for-9) with two doubles when swinging at the first pitch, compared to a 3-for-38 showing with a count featuring at least two strikes.

"That's what Chili is all about," manager Bob Melvin said. "You go up there aggressive, get ahead in the count, get a pitch to drive, they don't give it to you, you move on. But you don't go up looking for a walk. If the first pitch is there, and it's a first-pitch fastball and you can do something with it, have at it. We want them to be aggressive, everybody."

Barton has five hits in his past 13 at-bats, hitting safely in each of the last four games, after going 1-for-20 over his previous six contests. Perhaps not coincidentally, he's hit his stride just as he's started to gain back his everyday role at first base, due in part to a hamstring injury that forced Kila Ka'aihue to rest for a few days.

"This is probably the most comfortable I've seen him here, both defensively and offensively," Melvin said. "I think we're starting to make some strides with him. He's looking more confident.

"The way he's always been is a guy that works the count, who is a little less apt to swing early in the count. Now I think you're starting to see some first-pitch swings. Teams know what he's doing. If you're continually taking strike one and getting behind, that makes the road a little tougher, as far as the at-bat. If he shows them he can swing early in the count, maybe that makes them pitch him a little bit differently."

Worth noting

• It is still unknown when Yoenis Cespedes, sidelined by a muscle strain in his left hand, will begin swinging the bat again. Melvin said Monday is a possibility, one day before he's eligible to come off of the disabled list.

"Everything to this point looks good," Melvin said. "I think he would like to swing the bat at this point, but we're being a little cautious with him."