Seth Smith and Donaldson hit back-to-back home runs in the first inning off Seattle right-hander Hector Noesi, whose rough spring continued as he allowed seven runs [six earned] in two innings.
Donaldson was hitting .050 (1-for-20) coming into the game, but broke out in a big way with a 2-for-3 day with three RBIs on his two blasts.
Noesi, making his fourth Cactus League appearance, gave up five hits, two walks, a wild pitch and hit a batter while surrendering three home runs and throwing 52 pitches.
After going 2-12 with a 5.82 ERA last year for the Mariners, Noesi needed to show something this spring to compete for a rotation berth. But the 26-year-old, acquired in the Jesus Montero-Michael Pineda trade from the Yankees last year, instead has struggled out of the gate.
Former Mariners catcher John Jaso doubled off Noesi to start off the A's five-run rally in the first, with another double by Daric Barton following the homers by Smith and Donaldson.
Donaldson hit his second home run -- a two-run bomb -- in the second inning. Right fielder Shane Peterson added a solo shot in the third off Mariners reliever Chance Ruffin.
Mariners right fielder Casper Wells continued his red-hot week with a solo home run in the second inning off A's starter A.J. Griffin.
Griffin pitched three innings, allowing one run on four hits.
The game was officially called in the top of the fourth inning after the A's had runners on first and second after Michael Choice's two-run home run.
Up next for Mariners: Veteran right-hander Jon Garland continues his bid for a rotation berth with his third start of the spring when the Mariners travel to Glendale to face the Dodgers at 12:05 p.m. PT. Garland, who has been out of the Majors since shoulder surgery in 2011, has yet to allow a run while giving up three hits in three innings of work. He's slated to pitch the first three frames against the Dodgers, with left-hander Joe Saunders to follow with another three innings.
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.