Arizona Diamondbacks' Stephen Drew, right, slides safely under the tag of Colorado Rockies catcher Chris Iannetta during the game Monday.
Arizona Diamondbacks’ Stephen Drew, right, slides safely under the tag of Colorado Rockies catcher Chris Iannetta during the game Monday.

PHOENIX — Strong pitching is supposed to make the Arizona Diamondbacks a contender. Big bats made them a winner on opening day.

Tony Clark and Arizona newcomer Felipe Lopez each homered from both sides of the plate, and the Diamondbacks outslugged the Colorado Rockies 9-8 on Monday.

Eight home runs were hit in the game, including the decisive shot by Chad Tracy leading off the seventh inning against reliever Jason Grilli (0-1).

“It was a heavyweight fight out there. It was blow after blow,” Tracy said. “Every time we scored, they scored, and we finally had the last say.”

Lopez and Clark became the first switch-hitting teammates to homer from both sides of the plate in a game since Jorge Posada and Bernie Williams did it for the New York Yankees on April 23, 2000. It had never been done on opening day.

“Pretty amazing,” Diamondbacks manager Bob Melvin said. “Pretty phenomenal.”

Lopez, signed as a free agent in the offseason, is the first Arizona player to homer twice in his first game with the team. He is the first to do it in the majors since Richie Sexson for Seattle on April 4, 2005.

Troy Tulowitzki, Chris Iannetta and Seth Smith hit solo homers for the Rockies.

Arizona ace Brandon Webb was rocked for six runs and six hits in four innings. Rockies starter Aaron Cook fared even worse, allowing six runs and seven hits in 2 1-3 innings. Neither had command of their featured pitch, the sinker.

“I was up in the zone,” Cook said. “The sinker was flat and you saw what happened, just not a normal day for me and Webby, either.”

Webb said he was dropping his arm too low, and was bothered by stiffness in his shoulder early in the fourth inning, when he gave up consecutive homers on three pitches to Tulowitzki and Iannetta. He said he felt fine after the game, though.

Tony Pena (1-0) worked 1 1-3 scoreless innings for the win and closer Chad Qualls got three outs for a save.

“If they hit five home runs, you’re in a bad place. You’re struggling,” Colorado manager Clint Hurdle said of his pitchers’ woes. “I’m real proud of the way our offense battled back.”