Their bats could have more trouble Tuesday night against scheduled starter Zack Greinke, who appears to be finding his groove with the Angels.
Oakland's season-high nine-game winning streak was snapped with Monday's 8-3 loss. The A's (76-58), whose lead over Baltimore for the AL's first wild-card spot was trimmed to one, entered the series having averaged 10.0 runs in their previous six contests while clubbing 16 homers.
Donaldson has suddenly found his power stroke, homering four times in his last five games bringing his season total to six.
"The ability is there," Bob Melvin told the Athletics' official website. "We're getting a lot of production out of him."
The Angels (72-63), meanwhile, are starting to see the results from Greinke (3-2, 4.82 ERA) that they envisioned when they acquired him from Milwaukee before the non-waiver trade deadline.
Greinke has yielded three runs over 14 2-3 innings in winning his last two starts after recording a 7.20 ERA in his previous four.
"I was doing so bad, I figured I couldn't do any worse,'' the 2009 AL Cy Young Award winner said after allowing two runs and five hits in seven innings in Thursday's 5-2 victory over Boston. "The main thing (now) is I'm not worried about messing up. ... Better location, I guess that's the main thing. I'm not leaving my mistakes over the middle of the plate.''
The right-hander struggled mightily with his command in Oakland on Aug. 8, allowing four runs, six hits and five walks in five innings of a game the Angels lost 9-8.
Los Angeles has won six of seven - scoring at least five runs in each of those victories - and is 10-3 since Aug. 21 to pull within 3 1/2 games of a wild-card spot.
"When you play the team ahead of you, it's your best chance to make up ground,'' Vernon Wells said. "We know what's at stake. Right now, it's just a matter of if we do it collectively then we're going to win our share of ballgames. That's all that matters at this point.''
Wells, batting in the eighth spot, had a solo shot and RBI single Monday, while No. 9 hitter Chris Iannetta had a two-run homer as part of a three-hit day.
Iannetta and Torii Hunter, who hit his 13th homer in the opener, have been carrying the Angels' offense lately. Iannetta is batting .393 with three homers and 12 RBIs over his last 16 games, while Hunter is hitting .600 with three doubles and seven runs in the last six.
Iannetta is also 2 for 3 lifetime against scheduled starter Jarrod Parker (9-7, 3.72).
Parker wasn't sharp Thursday in Cleveland, giving up five runs, eight hits and three walks in five innings, but got more than enough run support in a 12-7 win.
The A's have won his last three starts, with the righty recording a 3.79 ERA and receiving 20 total runs of support. He had a 5.71 ERA in losing his previous three outings, while backed by one run.
One of those defeats came to the Angels on Aug. 6, when he gave up four runs in 6 2-3 innings of a 4-0 loss.