"I swung and missed on a slider and I felt something in my back," Gonzalez said. "I'll be playing tomorrow."
Rockies manager Walt Weiss said Gonzalez is day to day after suffering what he called a "strained upper back."
"He said he's done it before," Weiss said. "So we're not too concerned. But it was enough of an issue to get him out of there. So there is some concern."
Gonzalez remained in left field for the top of the sixth, but outfielder Corey Dickerson pinch-hit for Gonzalez in the bottom of the inning and replaced him in the field.
Gonzalez chased down an RBI double off the bat of Adrian Gonzalez in the sixth, slowing down as his feet touched the warning track and covering his head as the ball careened off the middle of the wall. Though not a routine play, Gonzalez did look hesitant to throw his body against the wall in an effort to make the run-saving catch.
"Seen him make some great plays out there," Weiss said. "I think it was bugging him."
The Rockies slugger leads the National League with 23 home runs and was 1-for-3 with an RBI double in the first before he left the game.
Ian McCue is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.