ANAHEIM -- For the second night in a row, the Red Sox made themselves right at home at Angel Stadium. The Angels, for their part, were more generous in their role as hosts than their leader would have liked.
"We shot ourselves in the foot on the defensive side," manager Mike Scioscia said following a 4-3 loss on Friday night in front of 39,005. "We just didn't make a couple of plays, uncharacteristically, and it cost us."
With Jon Lester delivering an emphatic early message by striking out the side in the first inning, Boston went on to pin the first defeat on Dan Haren, who'd won his first four decisions and was hoping to join teammate Jered Weaver at 5-0.
"I don't want to lose," Haren said, "but chances are I wasn't going to go 34-0. It's easy when things are going well. Character shows when they aren't. I'm looking forward to my next start on Wednesday [against Oakland]."
Boston manager Terry Francona admired Haren's effort.
"His stuff is tremendous," Francona said. "He's got deception. He throws strikes with that split, the cutter, the fastball. He's tough. And again, we made him work hard. That was part of the reason we won."
Two of the four runs charged to Haren were unearned, the result of a miscalculation by Peter Bourjos, the brilliant young center fielder.
With two outs and runners at second and third in the fourth inning, Boston leading 1-0, Haren got Carl Crawford to loft a seemingly harmless fly ball to shallow right-center.
Bourjos broke in but then pulled up, seeing second baseman Howard Kendrick and right fielder Torii Hunter converging on the scene. At the last instant, seeing that he was closest, Bourjos made an attempt at a basket catch, and the ball bounced off his arms for an error, making both runs unearned.
"It was kind of a 'tweener," Scioscia said, "but it was up there long enough that somebody should have been camped under it. [It was] not a Bermuda Triangle. Peter wasn't aggressive enough. There's a chance there's going to be some indecision. Peter's a tremendous center fielder; that's one play he's going to learn from."
Bourjos had opened the inning with a sensational running catch in left-center, depriving Adrian Gonzalez of extra bases.
Haren took that into account in absolving his teammate of blame.
"Pete's the only center fielder who gets to the ball Gonzalez hit," Haren said. "I couldn't believe he got there. There's not another center fielder who gets to that ball.
"He's playing tremendous outfield for us. It was just one mistake. If he keeps doing what he's doing, we'll be fine."
Haren was not as precise as he'd been, walking three hitters while getting saddled with a high pitch count by the Sox's disciplined band of hitters. He'd walked a total of two men in 31 previous innings.
Shut out by Lester (2-1) across six innings, the Angels also worked counts effectively enough to get into the Boston bullpen. They produced a run in the seventh against Matthew Albers when Erick Aybar singled with two outs, stole second and scored on Jeff Mathis' single.
Facing ex-Angel Bobby Jenks in the eighth, Kendrick doubled to right-center field leading off and scored as Bobby Abreu ended an 0-for-15 slide with a single to center.
After the thick night air swallowed deep fly balls by Hunter and Vernon Wells, Abreu scored from second on a passed ball when catcher Jarrod Saltalamacchia couldn't locate it in time.
Jonathan Papelbon secured Lester's win with his fifth save, Hank Conger's one-out pinch-hit single the only disruption.
The Red Sox struck first in the third inning when Saltalamacchia doubled to right-center off Hunter's glove. The catcher took third despite a sensational throw by Hunter on Marco Scutaro's fly ball.
After Scioscia protested the call by umpire Brian Gorman, Jacoby Ellsbury slashed an RBI double past first base.
"I thought he was out from my view," Haren said. "[Saltalamacchia's] thumb guard or something came out, and I don't know if that was mistaken for the ball or what."
A two-out walk to Jed Lowrie in the fourth inning proved costly. J.D. Drew followed with a double, Lowrie stopping at third. Haren appeared to be out of trouble when Crawford lifted his fly ball, but it turned into a 3-0 lead.
Haren walked the first two hitters in the fifth, but he escaped by striking out Dustin Pedroia and retiring Gonzalez and Ortiz.
In the sixth, Lowrie's leadoff double resulted in an error by Wells in left field when he bobbled it at the wall. Wells, errorless all last season as Toronto's center fielder, has already made two this year in the transition to left.
Drew's single through the middle scored Lowrie from third.
Lester had one rough spot in the third inning. Bourjos doubled with two outs and Kendrick worked a full-count walk after Bourjos stole third. Kendrick then stole second, but Abreu flied out to deep center.
Lester departed having given up four hits and two walks, striking out eight.
"It was good that we went back and forth and didn't allow them to sit one side, when they were swinging like they were," said Lester, whose fastball was his calling card.
Striking out six, Haren left after six innings with a 1.46 ERA. Only Weaver, at 1.23, has a better ERA in the American League.
The Red Sox's two wins represent an extension of its domination of the Angels last season. The Sox were 9-1, taking all three in Anaheim. The Angels' only win came in their final meeting at Fenway Park.
Lyle Spencer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.