OAKLAND – A sea of green and gold swelled, clamoring for more to the story that it cheered without trying to explain it.

The A's, written off widely before the season began, had won 14 home games in their final at-bat this year, raging against any finality that didn't come on their terms.

They beat it back again.

Down 3-1 and three outs from playoff elimination, the A's rallied against Detroit Tigers closer Jose Valverde to win 4-3 on Coco Crisp's walk-off single in Game 4 of the American League Division Series on Wednesday night.

Down 2-0 in the series coming back to Oakland, the A's have forced a winner-take-all fifth game. It will be Jarrod Parker against Justin Verlander tonight with a trip to the American League Championship Series on the line.

"Nothing surprises me with this team," right fielder Josh Reddick said, music blaring in the home clubhouse.

Reddick, 1 for 13 in the series as he stepped in to lead off the ninth, grounded a single into right field. Josh Donaldson then hammered a first-pitch fastball off the wall in left-center for a double, sending Reddick to third and the crowd of 36,385 into a frenzy.

"When we were in Detroit, he threw three fastballs right by me," Donaldson said of Valverde. "I wasn't going to let that happen."

Seth Smith laced a ball into the gap in right-center to bring both runners around, tie the score and, in the words of Crisp, "give me the opportunity to come up there and do something magical" after George Kottaras popped out and Cliff Pennington took a called third strike.

Crisp dropped a ball in Game 2 that led to two runs in a loss. He robbed Prince Fielder of a home run in Game 3 that preserved a shutout win. Crisp shot Valverde's first pitch into right field. Smith scored the winning run and the A's exploded onto the field, another day added to their improbable season.

"It's an unbelievable story, and it just keeps going," closer Grant Balfour said. "Oh man, that is one of the best feelings I've had in a long time, to know that we're going to go out and play (today)."

They were proofing the final pages as the A's struggled to figure out Tigers starter Max Scherzer's mid-90s fastball and biting slider, striking out eight times through five innings while the Tigers built a 2-0 lead against A's right-hander A.J. Griffin.

Alex Avila doubled down the right-field line to lead off the third, moved up on a bunt and scored the first run on Austin Jackson's single to left. The Tigers' second run was louder. Griffin left an 0-2 fastball over the plate to Fielder, who crushed it to right field, Reddick hardly moving as it sailed over his head into the seats.

But as Scherzer's night lengthened, his fastball appeared to lose steam. Leading off the sixth, Crisp battled for 10 pitches before hitting a one-hopper that bounced off Fielder's glove for a two-base error. Crisp then scampered to third on a wild pitch.

Stephen Drew, playing stellar defense for two nights, laced a double to right-center to score Crisp. But Drew tried for third, and Infante's relay of Jackson's throw from center reached the bag well ahead of Drew.

Manager Bob Melvin said Drew "went on his own. He thought he could make it."

Third-base coach Mike Gallego shouldered some blame as well, saying he wanted to be aggressive. Instead of the potential tying run on second base with no outs, the A's had nobody on and one out.

"Coaches make a mistake, players pick him up, and player makes a mistake, teammates pick him up," Gallego said. "Fortunately, we've got a (group) in here that nobody says die."

The Tigers added a run in the eighth on Avisail Garcia's run-scoring single to stretch their lead to two and put the game in the hands of their closer in the ninth.

"Everybody in the dugout was saying, 'Let's go, we believe,' " Donaldson said. "It's just happened so many times this season that it just feels like it's going to happen."

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