The Yankees fell back into second place in the American League East with the loss, snapping an eight-game road winning streak and taking just their third loss in their past 16 games overall.
It's an outcome that isn't particularly new in Anaheim, where the Bombers have dropped 15 of their past 20 games, but they were hoping for more in Chamberlain's 17th start of the season.
"You just want him to continue to improve," captain Derek Jeter said. "I'm sure he's going to get better once he gets some innings under his belt. I really don't think he pitched all that badly today. We gave them some extra outs and they scored some runs, but he expects a lot out of himself and we expect a lot out of him. He's going to be fine."
The evening started out on a promising note for the Yankees, as they scored three first-inning runs against left-hander Joe Saunders and staked Chamberlain to a 5-1 lead heading to the bottom of the fifth inning.
But Chamberlain has been unable to repeat his mechanics enough to duplicate a start of the caliber of June 1, when he hurled eight innings of two-run ball in a victory at Cleveland. Since then, Chamberlain is 1-2 with a 5.04 ERA and still struggling to recapture that magic.
"When you cut corners, you don't get as frustrated," Chamberlain said. "But when you're out here working your tail off trying to get better, watching video, doing the things that you need to do -- that's what's frustrating."
This time, Chamberlain came undone in the Angels' four-run fifth. Bobby Abreu stroked a run-scoring single and Alex Rodriguez committed a throwing error before Kendry Morales blasted a hanging curveball for a three-run, game-tying homer, sending the ball halfway up the ramp in center field.
"They're good hitters -- they're guys that have been here for a long time and know what to do," Chamberlain said. "They have a game plan going into it, and we executed our game plan well. They hit mistakes, but that's the nature of the beast. You've got to go out and be better."
Before that pitch, manager Joe Girardi had visited the mound with a message for Chamberlain -- not to think about the defense behind him.
"Get the hitter," Girardi said he told Chamberlain. "Let's make sure we concentrate on the hitter and not get caught up with anything else. He left a curveball up and he hit it out of the park."
With Chamberlain chased a batter later, the Angels took the lead in the sixth against reliever Mark Melancon, as Chone Figgins tripled to drive home Erick Aybar with the go-ahead run and Abreu tacked on another run-scoring hit to push the advantage to 7-5.
Errors were a theme for the Yankees -- just as Rodriguez's miscue served as a prelude to Morales' blast in the fifth, a rare dropped popup by Jeter in the seventh set up Aybar's three-run homer off struggling reliever Brian Bruney.
"I don't know how to fix it -- I'm trying," Bruney said. "It's the same thing I say every time. It's baseball -- I don't try to give up runs, I don't try to give up hits, I don't try to walk people. I'm doing my best every time out there, but it's just not working."
With Jeter on the way to his fourth four-hit game of the season, New York had given Chamberlain leads of three and four runs early in the contest. The Yankees put three on the board in the first inning, as A-Rod doubled home Jeter and Nick Swisher followed with a two-run single to left.
Johnny Damon added a run-scoring single in the second and Rodriguez belted his 15th home run in the fifth, a solo shot to dead center that stretched the Yankees' lead to 5-1. Saunders also exited after five innings, leaving the outcome to the bullpens.
"We need to get a better handle on our starting pitching," Angels manager Mike Scioscia said. "The only option is to come back offensively, and we're doing it. We swung the bats a notch above."
The Yankees' best late chance came in the seventh, when Melky Cabrera trimmed the deficit to one run with a run-scoring single to left off Kevin Jepsen. New York loaded the bases for pinch-hitter Hideki Matsui, who gave a Darren Oliver pitch a ride but watched it die just at the edge of the right-field warning track.
Girardi gave Chamberlain a vote of confidence after the game, saying that his past seven starts have not been "horrible" and noting that expectations are always high for this particular pitcher.
Girardi said the Yankees would keep working at the project, but he noted that results would need to be seen in the second half. The team is without right-hander Chien-Ming Wang, and its rotation is in a state of flux, as Alfredo Aceves flopped in a spot start Thursday and Sergio Mitre would seem to be next in line.
"It's important," Girardi said. "We need [Chamberlain] to pitch the way he's capable of pitching, because our fifth spot is up in the air. We want him to be successful so we can have options."