Oakland had only three hits in the game, but handed Los Angeles its third straight loss and gave C.J. Wilson his first setback in an Angels uniform.
The A's had a 1-0 lead going into the fourth but Wilson, obtained in free agency from Texas during the off-season, walked the first two batters of the inning.
Seth Smith put down a would-be sacrifice bunt that Wilson fielded, but the Los Angeles pitcher threw wildly to first. Both Yoenis Cespedes and Jonny Gomes dashed around to score on the play and Smith wound up on second.
Ka'aihue then drove in Smith with a single for a 4-0 Oakland advantage.
That was it for the offense for both teams, however, and five Oakland relievers held the Angels scoreless on three hits over the final four frames.
Tommy Milone (2-1) went five innings while giving up two runs on seven hits to get the win. Wilson (2-1) struck out eight over six innings and gave up all four runs, one of which was unearned.
Oakland's Grant Balfour worked the ninth for his fourth save.
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