Roy Ryan Dempster #46 of the Texas Rangers pitches against the Los Angeles Angels of Anaheim at Rangers Ballpark in Arlington on September 28, 2012 in Arlington, Texas.
Even though Ryan Dempster has spent less than two months in the American League, he already has a nemesis in the Los Angeles Angels.
Jered Weaver became the AL's first 20-game winner, Mike Trout hit a leadoff homer off Dempster and the Angels beat Texas 7-4 Friday night to prevent the Rangers from clinching a playoff berth.
The first-place Rangers had their lead in the AL West reduced to three games after Oakland beat Seattle on Friday night.
Texas' magic number remains at three to clinch its third straight division crown. The Rangers need one more victory to lock up a postseason spot.
Dempster (12-8) lost for the second time this month to Weaver and the Angels. In his third start against Los Angeles since being acquired July 31 from the Chicago Cubs, Dempster is 0-2 with an 11.20 ERA.
The right-hander allowed four runs and seven hits to drop to 7-3 since coming Texas.
"I didn't see him get as many balls up as he had in the past," Texas manager Ron Washington said. "He actually kept us in the ballgame. Give them credit, they swung the bats."
Los Angeles is two games behind Oakland for the last wild-card spot. The Angels have gone 25-10 since Aug. 21 to stay in the postseason chase, and Weaver has been big part of that run.
Weaver (20-4) has won his last four starts overall with a 1.98 ERA in 27 1-3 innings since Sept. 13.
The lanky right-hander allowed two runs and five hits in seven innings to beat Texas for the fourth straight time this season. He is the Angels' first 20-game winner since Bartolo Colon had 21 in 2005.
"We're not in a pennant race without him," Angels manager Mike Scioscia said. "You look at just what he's done virtually every start. I don't think there's a more consistent pitcher in our league."
Trout homered on the sixth pitch of the game out to the grassy area beyond the wall in center, his fifth starting off a game since Aug. 18.
The dynamic Angels rookie also set a club record by scoring his 125th run this season on that blast. It breaks the mark of 124 runs scored by Vladimir Guerrero in 2004.
"I feel like I'm putting good swings on the ball," Trout said. "I've got to go up there and battle."
Chris Iannetta hit a solo shot in the third for Los Angeles, and slumping outfielder Mark Trumbo had three RBIs and saved at least one run with a nice catch in left.
Nelson Cruz hit a solo shot in the seventh and Adrian Beltre added a two-run homer in the eighth that brought the Rangers within 7-4.
With two outs in the bottom of the eighth, right fielder Torii Hunter played Cruz's drive off the wall and threw him out at second trying to stretch it to a double.
Ernesto Frieri pitched a perfect ninth to pick up his 22nd save in 25 chances.
Weaver had struggled on the road against the Rangers in his career. He came into the game with a 3-7 record and a 5.05 ERA lifetime in Arlington, including a loss where he gave up eight runs on May 13.
Weaver, who struck out five and walked two, was pretty much in control from the start Friday. Weaver also got some help from two nice defensive plays.
With two men on base, Trumbo made a twisting catch on the warning track of Mike Napoli's drive to end the second.
Third baseman Alberto Callaspo leaned onto a short wall and lunged into the stands to snag Ian Kinsler's pop in the third.
"I thought we hit some balls hard," Washington said. "Trumbo made a spin around catch and happened to be in the right place. We just didn't catch any luck."
Trout and Iannetta's homers off Dempster gave the Angels a 2-0 lead.
Trumbo, who had been hitting .175 since Aug. 1 had an RBI double in the fourth and then added another run-scoring double with two outs in the sixth to make it 4-1.
"Solo home runs don't beat you," Dempster said. "It's the pitches you don't make with two outs."
Los Angeles extended its lead to 7-1 with three runs in the seventh, which was capped by Trumbo's RBI single.
NOTES: Texas RHP Mike Adams had an MRI on Friday and was diagnosed with a mild cervical strain. Adams, who has been battling soreness near his right shoulder, said he will be sidelined indefinitely. He allowed three home runs in the eighth inning of Texas' 9-7 victory over Oakland on Thursday. . Los Angeles righty Ervin Santana (9-12) will oppose Texas left-hander Derek Holland (11-6) on Saturday.