BOSTON – There was no number 13 on the back of the grey throwback jersey to identify who was wearing it. There was no mistaking the swing: the home run swing of Alex Rodriguez.

The New York Yankees slugger cleared the fences for the 631st time, passing former teammate Ken Griffey Jr. to take over fifth place on the career list. A-Rod helped beat the Boston Red Sox 6-2 Friday and spoil the celebration on the 100th anniversary of their first game at Fenway Park.

“It was a very cool ceremony,” Rodriguez said about the pregame introductions of about 200 former Red Sox players, managers and coaches. “They put on a great show, but the game was good, too.”

It was for the Yankees.

Eric Chavez hit two homers and Nick Swisher and Russell Martin connected once each, one day after Curtis Granderson hit three of the Yankees’ four homers in a 7-6 win over the Minnesota Twins — and exactly 100 years after the Red Sox beat the Yankees’ forerunner, the New York Highlanders, 7-6 in 11 innings.

Clay Buchholz (1-1) allowed all five homers in losing for the first time in 12 starts, although he went on the disabled list to stay last June 19 with a lower back strain.

He allowed four runs in each first inning of his other two starts. On Friday, he gave up only one run in the opening inning. But by the time he left after walking Granderson to lead off the seventh, he had allowed six runs on nine hits and two walks with just two strikeouts.

“He’s still building,” Boston Manager Bobby Valentine said. “He’s still getting his feet underneath him.”

The Yankees led 1-0 three batters into the game. Jeter reached on an error by second baseman Dustin Pedroia, who lost his popup in the sun. Jeter moved up on a wild pitch and scored on Rodriguez’s single.

They needed only three batters again to take a 3-0 lead in the second. Swisher led off with a homer, Raul Ibanez grounded out, and Chavez drove an 0-2 pitch into Boston’s bullpen in right-center. Chavez had only six at-bats before Friday.

David Ortiz cut it to 3-1 leading off the second with his second homer. But the Yankees stretched their lead to 5-1 on leadoff homers by Chavez in the fourth and Rodriguez in the fifth. They were the second homers of the year for both.

Josh Beckett also served up five homers in Boston’s second game of the year, a 10-0 loss at Detroit.

The Red Sox lost their fourth straight, a span in which they’ve been outscored 31-8.

“We’re a good team. We’re just not playing good baseball,” Adrian Gonzalez said. “It’s frustrating the way we’re losing.”