Donaldson, who is on his second Carter bat, is hitting .338 (24-for-71) with seven doubles, five home runs and 15 RBIs in 19 games since his recall on Aug. 14.
Carter has been nearly as hot, hitting .321 (26-for-83) over his last 24 games and has hit a home run in four of his last five games.
Donaldson said he broke the first bat and pleaded for one of Carter's batting practice bats. That's what he used Monday to hit a homer over the center-field fence.
"The ability is there," A's manager Bob Melvin said. "We're getting a lot of production out of him."
Meanwhile, Tommy Milone got out of a first-inning jam. He wasn't so lucky the rest of the game.
Milone allowed five runs on a season-high-matching 10 hits over a season-low three-plus innings.
"From the first inning on, I didn't feel comfortable and was struggling to keep the ball low," Milone said. "I forced myself to throw strikes and I left it up in the zone. I felt like the first few hits were just ground balls that found holes, and that's baseball. But it just got worse from there."
Milone (11-10) failed in his first attempt to tie an Oakland rookie record for wins in a season as he allowed four straight hits and two runs in the second inning. He struck out one and walked none.
"It was just being inconsistent," Milone said. "I was throwing strikes but not where I wanted. This is one of those games you forget about and just come back the next day."
Milone won his two previous starts, and had allowed five runs over the previous 19 innings. He has walked one or fewer in each of his last 13 starts and 20 of 26 overall.
"This is not what we're used to seeing from him," Melvin said. "They had some good at-bats off him right away and made him work pretty hard."
He gave up leadoff home runs to Torii Hunter in the third and Vernon Wells in the fourth. Pat Neshek replaced Milone following the Wells home run.
"We knew with him. He's going to be around the plate, and if he makes a mistake we have to capitalize on it," Wells said. "Guys had great approaches today. We have meetings every day against pitchers, and today it actually worked."
Neshek was greeted with a double by Chris Iannetta, but then retired five straight.
Tyson Ross threw 2 2/3 shutout innings in his first appearance out of the bullpen this season. He walked one and struck out three and may have found his niche.
"He pitched reasonably well," Melvin said. "That's a spot where you want to keep the game where it is and get some length. He did that."