OAKLAND, Calif. — The Texas Rangers' hopes for a third straight American League West title crashed to the ground Wednesday afternoon like the popup that Josh Hamilton let fall to the outfield grass in the decisive inning of the regular-season finale.Hamilton's miscue on a routine popup to center field capped a six-run fourth inning for Oakland and will become the symbol of the Rangers' final-week tumble from first place into the wild-card game.Ryan Dempster and Derek Holland couldn't hold a four-run lead in the fourth inning, and Oakland completed a remarkable surge to the West title with a 12-5 victory at a sold-out Oakland Coliseum.The Rangers, who led the division by four games with six to play, will play at 7:30 Friday night in the wild-card game against either New York or Baltimore. Those two AL East teams were scheduled to play Wednesday night. A Baltimore loss would send the Orioles to Rangers Ballpark for one game to extend their season.The Rangers could have to play at New York if the Yankees lose Wednesday and the Orioles win, and then the Orioles win a one-game tiebreaker to determine the AL East champion.The A's took the lead for good as Hamilton misplayed a Yoenis Cespedes popup that would have ended an already ugly fourth inning, but instead the gaffe allowed the two go-ahead runs to score. Hamilton drifted in as though he had the ball all the way, only to have it deflected off the top of his glove.The Rangers entered the inning with a 5-1 lead after scoring five times in the third.Michael Young, David Murphy and Geovany Soto had two-out RBI hits in the third against A.J. Griffin, who lasted only 2 2/3 innings. Ian Kinsler started the rally with a blooper to right to open the inning, and Josh Hamilton followed two batters later with another single.Adrian Beltre drove in the first run with a single to left, but the rally looked like it might fizzle after a force out on a dropped popup. But Young sent a line drive to right that hit the foul line for a double that scored Hamilton, and Murphy followed with a blooper to right-center that plated Nelson Cruz and Young.Mike Napoli was next, and his popup about 20 feet to the left of home plate drifted back into fair territory and was missed by A's catcher George Kottaras. Soto capitalized with a ground single up the middle to snap an 0-for-16 skid and put the Rangers up 5-1.But the A's didn't go quietly. Not even close.Dempster, who issued three hits and a run in the first, had retired eight straight before issuing a four-pitch walk to Brandon Moss to start the fourth. Josh Reddick followed with a double off the wall in right-center to score Moss, and Josh Donaldson and Seth Smith followed with singles to make it 5-3 and send Dempster to an early exit.Holland relieved and got the first two batters he faced, but Coco Crisp doubled off the right-field line to tie the game. After Stephen Drew walked, Cespedes lifted the popup to center that sent the Rangers on their way to the wild-card game.Oakland, which trailed by 13 games on June 30, scored one more against Holland in the fifth and four more against Alexi Ogando in the eighth as the Rangers' offense went silent. They just missed a chance for two more in the fourth when Cruz missed a two-run home run by about four feet and Young's line drive with runners at second and third was snared by Moss to end the inning.In the seventh, Beltre led off with his third single and went to third as Cruz followed with a double. But A's reliever Ryan Cook, working for a fifth straight day, got a grounder to third from Young and struck out Murphy and Napoli.