After winning the first two games in the series with the AL West-leading Rangers, the Angels allowed a season-high 15 runs on Thursday night in a 15-9 loss to Texas.
"It was kind of a momentum kill from how we played the first two nights to how we played these last two," manager Mike Scioscia said. "It's tough. It's a good team there and it's not a forgiving park if your guys don't hit their spots, and some of our guys in the pen had a tough time doing that."
The Angels were coming off a 11-10 loss in 10 innings on Wednesday that marked the first time since 1986 that they lost a game in which they held a three-run lead in extra innings.
They followed that up on Thursday with the bullpen giving up seven runs in 2 2-3 innings.
"At some point, we need to control the game on our terms, to get some guys to come out of the pen that are going to give us a chance to make some pitches and get some outs," Scioscia said.
Josh Hamilton drove in four runs and the Rangers offense bailed out Ryan Dempster in his Texas debut with 18 hits.
The Rangers broke an 8-8 tie after six innings when they scored four runs in the seventh, including Hamilton's two-run double, and added three in the eighth.
Hamilton hit .177 in July, but had his second four-RBI game of the season on Thursday. He has hit 10 RBIs in his past nine games.
"Basically I've said stop thinking about it, stop listening to everybody -- everybody's got something to say," Hamilton said. "Just go out there and play. React. Try to slow the game down again. It worked. There's nothing wrong with my swing, it's just about trusting myself, not being too aggressive and trying to slow the game down again."
Dempster allowed eight runs and nine hits in 4 2/3 innings. The Rangers acquired Dempster from the Cubs minutes before Tuesday's non-waiver trade deadline.
Roy Oswalt (4-2) threw two scoreless innings in relief for the win.
C.J. Wilson gave up eight runs and 10 hits in 5 1/3 innings. David Carpenter (0-1) took the loss for the Angels. Angels relievers were charged with 11 earned runs in 6 1/3 innings in the last two games of the series.
"The down side for me is obviously I gave up too many hits," Wilson said. "The upside is the offense was really awesome this whole series, and if we continue to swing the bats like that, our pitching will fall in line and all of us will be OK."
Texas leads Los Angeles by five games in the AL West.
Ian Kinsler went 3 for 5 and scored four runs and Elvis Andrus and Michael Young also had two hits and two RBIs as Texas finished with 18 hits.
Mitch Moreland and David Murphy hit back-to-back pinch-hit singles before Hamilton's double in the seventh.
Outfielder Torii Hunter led the Angels with three hits, two RBIs and a run scored. Kendrys Morales went 2 for 5 with a homer and two RBIs. Albert Pujols, Alberto Callaspo and Howie Kendrick added two hits each for Los Angeles.
Besides Dempster, catcher Geovany Soto and rookie first baseman Mike Olt made their Texas Rangers debuts.
Soto went 2 for 5 with two RBIs and two runs scored, and Olt, a rookie from the University of Connecticut, went 1 for 3 with a run scored.
NOTES: Mike Olt was called up from Double-A Frisco Thursday and made his major league debut at first base just hours later. Rangers manager Ron Washington said Olt will mostly start at first base and also at designated hitter against left-handed starters. Olt can also play third base when Adrian Beltre has a day off. ... Angels outfielder Mike Trout was selected AL Player of the Month and AL Rookie of the Month for July. He's the first AL player to win both Player of the Month and Rookie of the Month in the same month. Trout also won the monthly rookie honor in May and June, joining Ichiro Suzuki (April, May and June 2001) as the only player to win in three straight months.