Buster Posey countered Miguel Cabrera's two-run homer with one of his own in the sixth inning, and Delmon Young answered with a solo shot in the home half to tie Game 4 of the World Series, 3-3.
Cabrera's blast in the third gave the Tigers their first lead of the Series -- a 2-1 cushion that lasted until the Giants' Posey stepped in three innings later.
Posey, the National League batting champion and like Cabrera an MVP candidate, turned on Max Scherzer's hanging changeup and smacked it just inside the left- field foul pole to silence the Comerica Park crowd. Marco Scutaro had led off the sixth with a chopper down the third-base line and easily beat Cabrera's double-pump throw to first.
Matt Cain retired Cabrera and Prince Fielder in the home half before Young smacked a first-pitch slider over the wall in right to give the Tigers life in a Series they trail, 3-0.
Detroit is trying to become just the fourth team to extend the Fall Classic after losing the first three contests. Twenty of the previous 23 teams to hold a 3-0 advantage have completed their sweeps, while the others have finished the series in Game 5.
The Giants, currently riding a six-game winning streak, went ahead on Brandon Belt's RBI triple in the second inning, but Scherzer stranded Belt at third and left runners on the corners an inning later.
Both Scherzer and Cain have allowed seven baserunners over six innings, with the former striking out eight.
Cain, who is trying to become the third pitcher in MLB history to earn a victory in three clinchers in a single postseason, shook off a two-out walk to Cabrera in the first inning and retired three straight after Young led off the second with a line-drive single.
Austin Jackson took a payoff pitch just out of the strike zone to earn a one- out walk in the home third, then advanced to second when Quintin Berry bunted to the third-base side and was thrown out by a step.
Cabrera, the American League's Triple-Crown winner, gave the home crowd something to cheer about when his wind-aided fly ball carried into the right- field bleachers to give the Tigers their first lead of the Series.
Detroit had not scored since the ninth inning of the opener, and the Giants had not trailed since losing Game 4 of the NL Championship Series to the Cardinals, a span of 56 straight innings -- four shy of tying the record for a single postseason.
San Francisco took its first lead in their half of the second when Hunter Pence hit a ground-rule double off and raced home on Belt's triple to right field.
Scherzer retired Gregor Blanco and Ryan Theriot to keep Belt from scoring, then got Posey on a flyout to center to leave a pair in the third.
Gerald Laird, filling in for an injured Alex Avila behind the plate, threw out Belt trying to steal second in the fourth inning.