Houston leads the best-of-five series 2-1 and can advance to its fourth straight AL Championship Series with a victory in Game 4 on Thursday.
The Astros wasted leads of 2-1 and 7-4, and the Athletics bounced back after giving up advantages of 1-0 and 4-2.
Houston's bullpen had stifled Oakland in the first two games with seven shutout innings of one-hit relief, but Pinder ended that dominance.
Houston led 7-4 when Marcus Semien and Tommy La Stella had back-to-back singles off Josh James starting the seventh. Pinder hit a first-pitch slider to the opposite field for Oakland's fifth homer, a drive chased by right fielder Kyle Tucker until he ran out of room at the short wall.
La Stella, Mark Canha, Matt Olson and Semien also homered for the A's, whose entire infield went deep. Teams outhomering opponents are 18-0 in the postseason.
The teams have combined for 18 homers - including seven in Game 3 - in the neutral-site series at Dodger Stadium featuring all day games. After two straight days in the 90s, the temperature cooled to 81 degrees.
Loser Brooks Raley walked Robbie Grossman leading off the eighth, and Ramon Laureano doubled. Murphy's sacrifice fly put Oakland ahead, Semien walked,
La Stella was hit on his right forearm, loading the bases and forcing La Stella from the game. Pinder, who went 3 for 4 with four RBIs, followed with another sacrifice fly in the eighth.
Winner Liam Hedricks pitched three innings of one-hit, scoreless relief.
Carlos Correa singled leading off the bottom of the eighth and Tucker reached on catcher's interference by Murphy, a call the A's challenged unsuccessfully.
Yuli Gurriel popped out, Aledmys Díaz advanced the runners with a groundout, and pinch-hitter Josh Reddick struck out, smashing his bat on the ground and breaking it over a knee.
Houston took a 7-4 lead with five runs in the fifth, when the Astros sent 10 batters to the plate. Díaz hit a tying, two-run homer off rookie starter Jesús Luzardo, and Brantley, Bregman and Tucker drove in runs. Houston was slowed when José Altuve was thrown out on a relay by Olson at first when he tried to go from first to third on Brantley's single.
Both starters allowed up four runs and five hits in 4 1/3 innings Luzardo and Houston's José Urquidy.
Zack Greinke's right arm is structurally sound and the Astros say they are hopeful he can pitch at some point in the postseason. The right-hander started Game 1 of the AL wild card series on Sept. 29, but was lifted after allowing one run and two hits and three walks in four innings. Greinke tailed off late in the season, posting a 5.73 ERA over his final seven starts; in that span, dating to Aug. 23, he gave up at least three runs in each outing. He off flat ground after the Astros' win in Game 2 and manager Dusty Baker said he was told the session went "pretty good."
ASTROS IN THE 2020 POSTSEASON
- Springer deepens his history at Dodger Stadium in ALDS Game 2 win
- Astros score 10 runs on hated rival Oakland to take Game 1
- Houston's Wild Card sweep of Minnesota sets up ALDS with A's
- Astros steal Game 1 of Wild Card series in Minnesota
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