Manager Bob Melvin said he's trying to find the two left-handers the best matchups. Ka'aihue, who's batting .412 against lefties, started the second of a three-game series against the Red Sox and southpaw Felix Doubront on Tuesday.
"It's a tough one right now," Melvin said. "To this point, Kila's had the better at-bats. He really has swung the bat well for a guy you didn't envision being in this spot right now. We really look for Daric to get a little more comfortable here and try to get him some matchups to get his confidence up and get him going. It's kind of a day-to-day thing with those two right now."
Barton has just five hits in his last 33 at-bats after going 4-for-16 over his first five contests. Overall, he's batting just .184 on the season, with a dismal .286 on-base percentage. He has seven walks to his name, but he also has 11 strikeouts -- one of which came Monday night with the bases loaded on a 2-2 pitch for the third out in the seventh inning of an 11-6 A's loss.
"There were some instances yesterday maybe he could be more aggressive, but if he draws a walk in that bases-loaded situation, too, it's another run and another baserunner," Melvin said. "You don't want someone to get completely out of their game, but to an extent know when there's a time to be more aggressive."
Ka'aihue figures to see more playing time should Barton's struggles, which have extended to his defensive game, continue. Barton, normally an above-average defender, has had troubles snagging throws in the dirt he'd normally have easily.
"When he's playing really well, he probably picks most of those," Melvin said.
"Confidence goes a long way in every facet of your game," he continued. "He's just not there yet completely in what he's doing, and maybe it filters into your defense some. We feel like he's going to get there."