SAN DIEGO — The pitching matchup was a thing of beauty, housed in a spacious, forgiving ballpark, played under a brilliant California summer sun.

Josh Beckett entered the duel as the American League’s winningest pitcher. His opponent, Jake Peavy, went into yesterday leading the National League in the same category.

But Beckett enjoyed one significant edge: He didn’t have to face the Red Sox lineup; Peavy did.

The Red Sox offense, while spotty of late, succeeded in wearing Peavy down and running his pitch count up. When he left after just five innings, he had thrown a staggering 111 pitches. Along the way, the Sox strung together three runs in the third, then tacked on another against the bullpen, capping a 4-2 win for the Sox over the San Diego Padres.

“Obviously, he’s one of the best in the game,” said Boston manager Terry Francona of Peavy, “and we made him work hard. Fortunately for us, one of the other best (pitchers was) on our team. And he was great. He had to be.”

That’s because, with Peavy as an opponent, Beckett’s margin for error was slim. So Beckett made very few mistakes, shutting out the Padres in seven of the eight innings he pitched. A two-run, pinch-hit double from Termel Sledge in the fifth was the only mark against him.

“Anytime you go against Jake Peavy,” said Beckett, baseball’s first 11-game winner, “it’s going to be a tough day. We were fortunate to a get a couple of big hits.”

In the third, the Sox strung together three consecutive singles to right from the top third of their order — Coco Crisp, Alex Cora and David Ortiz. Crisp scored on Ortiz’s hit, while Cora was delivered on a sacrifice fly from Manny Ramirez.

Two more singles followed from J.D. Drew and Mike Lowell, with Ortiz sliding in just ahead of the throw from outfielder Jose Cruz. Jr.

“We tried to make him elevate,” said Lowell. “He’s got a good sinker and he’s an elite pitcher, but we were able to string together a lot of professional at-bats against him.”

“These guys just grind,” said Beckett of his teammates. “Not many guys get through five innings with 95-100 pitches. We grind at-bats out and wear people down.”

The Sox managed just five more hits over the final six innings, but one was a solo homer to center by Jason Varitek off Scott Linebrink, giving the Sox some cushion.

The victory lifted the Sox’ lead in the A.L. East to 11 games over second-place Toronto. The Yankees, who dropped back under .500 with their loss at San Francisco, are in third place.

Beckett, who remains unbeaten (6-0, 1.14 ERA) on the road, got into his only jam in the fifth inning. He issued a walk to Kevin Kouzmanoff to start the inning, then yielded a single to center to Geoff Blum.

The Padres sent up Sledge to hit for Peavy and the outfielder stroked a double to the gap in right-center, scoring both baserunners. After a groundout moved Sledge to third with one out, the Sox brought the infield in and kept Sledge anchored at third when Michael Barrett grounded out to Julio Lugo at short.

Beckett then ended the inning by overpowering Adrian Gonzalez for the third out.

“I definitely didn’t want to waste (the run support) the guys gave me,” Beckett said. “I wanted to make every pitch count. I threw a lot of fastballs on the outer half and mixed in some changeups and curves.”

Beckett credited a mechanical adjustment he made Friday in a side session as a key to his success. Pitching coach John Farrell, in conjunction with a former catcher at home in Texas, noticed that Beckett was collapsing in his delivery to the plate.

“I was throwing a little uphill the last few games,” he revealed, “so I really worked on powering the ball down (in the strike zone) with some angle to it. It was just one of those adjustments you make.”

That helped produce 8 groundball outs from among the first 16 he recorded. In the seventh, however, he left a pitch up in the zone to Kouzmanoff, who seemingly crushed it to left. But Ramirez drifted back and made the catch on the warning track.

“That was one of those deals where I thanked God we were playing here (in a roomy outfield),” Beckett said.

And that Peavy was the one facing the more disciplined and discerning lineup yesterday.

smcadam@projo.com