GOODYEAR, Ariz. — Cincinnati Reds left-hander Aroldis Chapman has run into his first setback of spring training, and it has nothing to do with his control.

The Cuban defector left the game early Monday because of a stiff lower back, which has been bothering him for several days. The Colorado Rockies scored four times in his final inning and pulled away to a 9-1 victory.

Brad Eldred went 3 for 4 with two homers and three RBIs for Rockies.

The 22-year-old Chapman has been the talk of the Reds’ camp with a fastball that has been clocked at 100 mph. He dominated Milwaukee batters in his previous outing last Wednesday, striking out five in three innings while giving up only one hit. His strong showings made him a candidate for the fifth starter’s spot.

The back problems could change that equation. After an examination, the Reds said he was having back spasms.

“I’m not hurt,” Chapman said, speaking through a coach acting as a translator. “I had a little stiffness in my lower back. It has been bothering me for a couple days. I was able to work through it in the first inning, but it didn’t get loose in the second inning.”

Manager Dusty Baker visited the mound after he sensed Chapman holding back on his fastball.

“He didn’t say anything,” Baker said. “In Cuba, you know they are taught not to complain. You could tell he was wincing. He wasn’t throwing his fastball and he was shaking off the catcher to get to his breaking ball. We could tell something was wrong. We had to draw it out of him.”

Bronson Arroyo pitched the first five innings, allowing the first of Eldred’s home runs. Chapman got into the game in the sixth, with manager Dusty Baker planning to let him finish the game.

The left-hander pitched a perfect sixth, but gave up a pair of walks and a pair of hits in the seventh before leaving as a precaution. An error set up Jordan Pacheco’s three-run double, helping Colorado score four unearned runs in the inning.

The left-hander said it was more difficult to throw his fastball because of the stiff back.

“There was less effort to throw my slider than my fastball,” Chapman said. “I’ve never had back problems before.”

Arroyo gave up three runs and four hits in five innings, including Eldred’s solo homer and a two-run shot by Clint Barmes.

“I had better command than the last few times,” Arroyo said. “In this dry air, it’s one or the other — my breaking ball is no good or my changeup doesn’t have any sink. Today I didn’t have any sink on my changeup, but my breaking ball was OK. Last time it was flip-flopped.”

Jorge De La Rosa gave up a leadoff homer to Drew Stubbs. He allowed three hits in 5 1-3 innings, striking out five. Cincinnati managed only five hits overall.

Manager Jim Tracy is pleased with how the Rockies’ camp has gone so far.

“We’re just getting ready,” Tracy said. “We’re just doing our thing from day to day and having a ball. We didn’t want to make a lot of changes. We just wanted to work very hard on trying to perfect what we do.

“We wanted to build on what we felt good about the last 4 1/2 months. Can we run the bases better than we did last year? Can we put the ball in play more with two strikes? So far, we’ve been doing that.”

Notes: Ryan Spilborghs tripled off Arroyo in the first inning, his second triple of the spring. … The Rockies have at least one triple in each of the past six games. … Eldred’s homers were his first of spring training. … After the game, the Reds optioned OF Chris Heisey to Triple-A Louisville and reassigned INF Zack Cozart and IF/OF Todd Frazier to their minor league camp.