His back tightened after Monday afternoon's game, when his eighth-inning solo shot gave the Rockies a 4-3 victory over the Reds. Although his injury is not thought to be as bad as shortstop Troy Tulowitzki's -- he is experiencing spasms in the area -- Stewart was not in Rockies manager Jim Tracy's lineup against the Reds on Tuesday night.
"I've never had anything with the back," said Stewart, who has 23 homers -- one fewer than team leader Tulowitzki. "It's very surprising and disappointing for me. But I don't think it's anything that's going to linger or at least I hope not."
Stewart reported feeling better on Tuesday afternoon after going through electronic stimulation, massage and walking in the indoor pool at Coors Field.
As for Tulowitzki, Tracy said he is on some anti-inflammatory medicines, but until the tightness and spasms subside, he won't be under consideration for returning to the field. On Tuesday, Eric Young Jr. led off and played second base, Clint Barmes moved from second base to short and Garrett Atkins started at third base.
The Rockies' games are important. They entered Tuesday leading the National League Wild Card race by two games over the Giants and trailing the NL West-leading Dodgers by 3 1/2 games. But the team is not pushing Tulowitzki into the lineup, especially at his position.
"When [the spasms] let go, he's going to get immediate relief, but until it does, he's going to be stiff and sore and his mobility is not going to be good enough to think about or even talk about utilizing him," said Tracy, who admitted that the fact the Rockies are being chased rather than doing the chasing makes it easier for him to wait for an injured player to return.
Tulowitzki suffered a similar injury during Spring Training. His back stiffened after a long bus ride.
"It feels like that, as far as when I bend down," said Tulowitzki, who said he feels better than he did immediately after suffering the injury on an RBI single on Monday. "To get back up is a little tough. It's a little different, too, because [this time], I did it actually swinging."
Tracy also said right-hander Ubaldo Jimenez, who experienced hamstring tightness on Sunday while pitching six innings (three runs and three hits) and not figuring in the decision, likely will have his next bullpen session pushed back from Wednesday to Thursday. He scheduled to start Saturday on the road against the Padres.
The rotation is already missing right-hander Aaron Cook, who is out with a sore right shoulder and trying to find a way to pitch again before the regular season ends.
The Rockies planned to reevaluate center fielder Dexter Fowler on Tuesday and activate him for Wednesday night's game against the Reds.
With Double-A Tulsa and Triple-A Colorado Springs having fallen short in their bids for the playoffs, the Rockies called up outfielder Matt Murton, shortstop Mike McCoy and right-handed pitchers Jhoulys Chacin and Matt Belisle to the active roster on Tuesday.
In addition, the club is carrying two right-handed pitchers -- Samuel Deduno, the Texas League Pitcher of the Year at Double-A Tulsa, and Esmil Rogers, who spent most of the year at Tulsa but finished at Colorado Springs. However, Tracy said Deduno and Rogers aren't on the active roster.
Thomas Harding is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.