"I'm a little bit worried because I don't want to miss a start," Chacin said while wearing a wrap around his lower back. "I want to keep pitching, especially with how we're playing now. Everything is going well and I just want to keep helping my team."

Troy Tulowitzki hit a two-run homer and Chacin helped himself by driving in a run with a sacrifice fly as the Rockies won their seventh in row and remained unbeaten in seven home games this season.

Chacin (3-0) grabbed his lower left back after throwing his fourth pitch to Arizona's Cody Ross with one out in the seventh inning. He was taken out of the game after a brief conference near the mound with manager Walt Weiss and team trainers and replaced by reliever Wilton Lopez.

"We hope it's nothing serious," said the Rockies' Chris Nelson, who scored on Chacin's sacrifice fly after tripling to lead off the fifth. "But when you see your pitcher walk off the mound like that, it's a rough one for the whole team."

The team said Chacin, who allowed three hits in 6 1/3 innings and struck out five, exited the game with left oblique stiffness and would be re-evaluated Saturday.

Chacin was pitching a gem before the injury.

"I was throwing my fastball and my sinker down in the zone, attacking the hitter," he said. "I threw a lot of first pitch strikes and that really helped me."

But he felt a twinge on his 99th pitch and and a painful pull on his 100th.

"I don't know how bad it is," he said. "They'll see tomorrow how it is. I feel better now, but it was really painful when I threw the ball."

The last time a Colorado starter reached the century mark in pitches was last June 12, a stretch of 117 games. It was the longest string in the majors since records started being kept by STATS in 1988. Before the Rockies' streak, the longest string of starters not throwing 100 pitches in a game was held by Washington, which went 33 games from Aug. 31, 2011, to April 10, 2012.

"He threw all of his pitches over for strikes," Diamondbacks manager Kirk Gibson said. "We never really got ahead of him. He got the slider over alot early in the count and we laid off of that. He had good depth to it. That's probably the best I've seen him throw."

Chacin faced the minimum through four innings, inducing Paul Goldschmidt to ground into an inning ending double play after allowing his first hit, a single by Gerardo Parra, to start the fourth.

In the fifth, Chacin worked out of a two-out, bases-loaded jam by fanning his Arizona counterpart, Ian Kennedy. The Diamondbacks got an unearned run on third baseman Nelson's throwing error in the ninth before Rafael Betancourt closed the game out for his sixth save in six chances.

Kennedy (1-2), who allowed three runs on three hits in six innings, was overpowering early. He retired the first 10 batters he faced, half of them on strikeouts. With one out in the fourth, Josh Rutledge became the first Rockies batter to reach when he drew a walk.

After Carlos Gonzalez struck out, Tulowitzki got hold of Kennedy's first offering and drove it over the left field wall for his fifth home run of the season. He had come into the at-bat hitting .166 in 18 plate appearances against Kennedy, though it was his second homer off the Diamondbacks' starter.

"I had to be pretty much perfect because Chacin threw a pretty good game," Kennedy said. "He kept us off balance. Tough to win that one with someone throwing like that."

Game notes

Diamondbacks batting coach Don Baylor, who was the Rockies' inaugural manager and led them to their first postseason berth in 1995, was inducted Thursday into the Colorado Sports Hall of Fame. ... Nine of Tulowitzki's 15 RBIs this season have given the Rockies a lead. He hit a homer in consecutive games for the second time this season. ... Kennedy has lost consecutive starts against the Rockies after being 3-0 in four previous matchups.