BOSTON – David Ortiz’s first-inning homer helped the Red Sox open a big early lead and gave the Boston fans a chance to watch the Celtics in the NBA finals.

Clay Buchholz didn’t mind it, either.

“That’s big, going out to a three- or four-run cushion,” Buchholz said Tuesday night after pitching Boston to a 6-3 victory against the Arizona Diamondbacks.

“He’s a key to the success of this team. Whenever that guy’s hitting, it’s just a different lineup.”

Buchholz (9-4) allowed three runs on seven hits and a walk, striking out eight in 52/3 innings for his sixth win in seven starts. Jonathan Papelbon pitched the ninth to earn his 14th save and send the Diamondbacks to their 11th straight road loss.

Ian Kennedy (3-4) gave up six runs on nine hits and a walk, striking out six in six innings while also throwing two wild pitches and hitting a batter. He is 0-3 with two no-decisions since May 19.

“I don’t know if he was pitching away from the Monster or if he was trying to be fine when he was going away from these guys,” Diamondbacks Manager A.J. Hinch said. “When they get their arms extended, it’s pretty lethal.”

Dustin Pedroia, who batted .213 in May, had a pair of hits and scored three runs. He is batting .310 in June, with multiple hits in four of his last five games.

“That’s the last guy I worry about,” Ortiz said.

Pedroia was hit by a pitch in the first inning, and Ortiz followed with his first homer since June 2 — his 13th of the season. In the third, Pedroia doubled in a run, Daniel Nava scored on a wild pitch and then Pedroia scored to make it 5-1 on an infield single by Victor Martinez that resulted in a close play for first-base umpire Jim Joyce.

Replays showed Joyce was right.

The Fenway Park crowd began a “Beat L.A.!” chant right around tipoff time for the Game 6 of the NBA finals between the Celtics and Los Angeles Lakers. It was 6-3 in the fifth when empty seats began appearing.

It also helped calm down Buchholz.

“It’s a good way to play,” Red Sox Manager Terry Francona said. “When your pitching’s holding them, every time you score after that (helps).”

Arizona scored two in the fourth to make it 6-3 when Miguel Montero doubled and took third on Chris Young’s single. Young stole second and they both scored on Justin Upton’s double.

But Pedroia singled to start the bottom of the fifth, moved up on a groundout and scored on Kevin Youkilis’ double.

“After the fourth, we didn’t do much after that,” Hinch said. “(Buchholz) settled in and made pitches. He lasted long enough to hand the ball to their bullpen and they completely shut us down.”

Youkilis let Montero’s first-inning grounder go through his legs at first base — his first error of the season and first at first base since April 8 of last year.

But he also made two nice plays to field grounders to his right in the second inning, tossing to Buchholz at the bag for a putout reminiscent of Joyce’s blown call that cost Detroit’s Armando Galarraga a perfect game. Neither one was as close as Martinez’s infield hit on a grounder to shortstop in the third inning.