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SAN FRANCISCO -- Terry Francona has learned a lot about his team's perseverance this season. As the Red Sox have lost star player after star player to injury along the way, they have grinded out wins with others filling the void.

This time, it was Scott Atchison -- with a big assist from Mike Cameron's bat and glove and the rest of the bullpen -- on an afternoon Boston was dealt a double-whammy.

Second baseman Dustin Pedroia went on the disabled list with a broken left foot, then a few hours later pitcher Clay Buchholz left his outing after only one inning with a hyperextended left knee.

Cameron hit a three-run homer, Darnell McDonald also connected and the Red Sox beat the San Francisco Giants and their top pitching prospect 4-2 on Saturday.

"We've played with so much better personality the last month and a half," Francona said. "It's a good feeling. This team's forming its own personality."

Atchison (1-1) tossed 2 1/3 innings for the win against his former team after Buchholz got hurt while running the bases. The Red Sox used seven relievers to pull this one out.

"That was the bullpen's win today," said Buchholz, who hopes to make his next turn even if it's pushed back because of two upcoming days off. "They did what they had to do on 30 seconds' notice. Atch started it."

The Giants called up Madison Bumgarner (0-1) from Triple-A Fresno to make his 2010 debut and second career start. He struck out five and allowed four runs and five hits in seven innings, but had to throw a lot of pitches to get through Boston's dangerous lineup. He didn't get much help from the offense, either.

Buster Posey drove in both Giants runs but that wasn't enough as the Red Sox rebounded to even the series following a 5-4 loss Friday night.

Along with his first home run in a season that featured more than a month on the disabled list with an abdominal strain, Cameron crashed into the wall to make a great catch of Pablo Sandoval's fly to end the eighth.

While Francona ranked the defense ahead of the long-awaited longball, Cameron was happier with the homer.

"Hell, yeah," he said. "That's big. I've come close. I think I got snake bit off the walls in Fenway a couple times. ... I knew I hit it good but I hit it good in Colorado and it didn't go out. I was starting to doubt I still had a little pop in my bat."

Jonathan Papelbon worked a 1-2-3 ninth on eight pitches for his 17th save in 20 chances.

Buchholz singled in the top of the second and was apparently injured moments later running between first and second on Marco Scutaro's inning-ending double play. Buchholz, Boston's only pitcher with double-digit wins, grabbed his left hamstring in the dugout.

In the middle of the game, the Red Sox announced they had acquired infielder-outfielder Eric Patterson from Oakland for minor league pitcher Fabian Williamson.

Getting Patterson gives Boston some added depth with Pedroia out. Patterson was initially set to join the team Sunday, an easy trip considering the A's are playing at home across the bay against the Pirates, but Francona said he would instead meet the Red Sox on Tuesday in Beantown.

The 20-year-old Bumgarner was scratched from a scheduled start Friday night for Fresno at Portland in case the Giants needed him Saturday. With Posey getting a rare start behind the plate, San Francisco had two of its top rising stars in the lineup.

Posey had an RBI groundout in the fourth and a sixth-inning sacrifice fly.

Bumgarner walked just one batter in a 96-pitch outing and singled leading off the fifth for his first major league hit.

The left-hander, who went 7-1 with a 3.16 ERA in 14 Triple-A starts this season, is expected to remain in the rotation as the Giants try to find some consistency from their No. 5 starter. Todd Wellemeyer isn't close to returning from a strained right quadriceps that sidelined him June 11 and should keep him out until the All-Star break or longer.

Bumgarner was nervous, and the fact it was the Red Sox stepping in against him added to the pressure.

"Even though I've been here and threw a couple of times, there's still a lot of nerves going through the body. It's just a tough thing to deal with," he said. "I was pleased with the last half of the game, that's for sure."

Bumgarner also took the mound shortly after the Giants retired the No. 20 of 91-year-old Hall of Famer Monte Irvin -- with Hall of Famers Willie Mays, Willie McCovey, Juan Marichal, Gaylord Perry and Orlando Cepeda on hand -- offering quite a glimpse of Giants past and future.

Game notes

Red Sox RHP John Lackey, Tuesday's starter at Fenway Park against Tampa Bay, grounded out as a pinch-hitter in the fifth. ... San Francisco on Sunday will honor its pitchers with no-hitters, including current starter Jonathan Sanchez as he approaches the one-year anniversary of his July 10 gem vs. San Diego. ... The Giants optioned RHP Joe Martinez to Triple-A Fresno to make room for Bumgarner. ... Williamson was 4-3 with a 3.72 ERA in 14 starts for Class-A Salem. Boston's 40-man roster is now at 40. ... Giants 2B Freddy Sanchez was rested before a pinch-hit double to start the seventh. ... San Francisco drew 42,178 fans for its 10th sellout this season.