Leading off the second, Tigers cleanup hitter Fielder flied out to the warning track in left. He was robbed of three hits a night earlier, including on Coco Crisp's leaping catch at the top of the center-field wall to save a home run.
Detroit had only one RBI via hit in the first three games, on Alex Avila's solo home run in a 3-1 Game 1 win at Comerica Park.
Avila doubled against Griffin to start the third and advanced on Omar Infante's sacrifice before Jackson drove him home.
Leyland made a few tweaks to his lineup Wednesday against a right-handed starter after facing lefty Brett Anderson a night earlier.
Josh Reddick, who led the A's with 32 home runs this season, struck out to start the second to give him seven Ks so far in the four games. That tied the most by an Oakland player in a postseason series.
The A's shut out the Tigers 2-0 on Tuesday night but have never come back to win a series when trailing 2-1.
Yet this no fear Oakland team erased a five-game division deficit over the final nine games of the regular season to stun the two-time reigning AL champion Texas Rangers in Game No. 162 one week ago.
Game 1 winner Justin Verlander would pitch Game 5 on Thursday night if needed, against Parker.
At 24 years and 256 days, Griffin became the sixth-youngest pitcher in Oakland history to make his first postseason start.
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