Suddenly, another big night for Troy Tulowitzki was just an afterthought.
However, manager Jim Tracy said Cook's season may not be finished just yet. He intimated there remains a chance the franchise's career leader in wins could be back on the mound.
"We're going to have to deal with that and see where it takes us, as far as a time frame and things like that," said Tracy, whose club matched their longest winning streak of the season.
Cook hobbled around the mound for a few minutes after he was struck, then gingerly walked off the field and into the dugout. The team reported the injury as a bruise, but X-rays revealed it was more serious.
"That breaks your heart that something like this would happen to him," Rockies pitching coach Bob Apodaca said. "You hate to see it happen to somebody that's worked real hard to get back into a position to really be a contributor."
Cook (6-8) was cruising before the injury, allowing one run and six hits in five-plus innings. It was his second straight win since coming off the disabled list with a right big toe ailment.
"He was commanding the strike zone like the Cook of old and was getting ground balls consistently," Apodaca said, shaking his head. "How do you explain something like this, the timing of it?"
Tulowitzki provided the bulk of the offense, hitting a three-run homer in the third and a solo shot two innings later for his second career multihomer game.
Seth Smith had a solo shot while youngsters Jonathan Herrera and Eric Young Jr. each delivered a two-run single. Carlos Gonzalez extended his hitting streak to 16 games with a bloop single in the sixth.
With the win, Colorado remains 4½ games behind the Atlanta Braves in the NL wild-card race.
Despite their fourth straight loss, the Reds still lead the NL Central by six games over St. Louis. The Cardinals lost 8-1 at Milwaukee.
"Another chance to pick up the game, but you've got to look at the bright side," Reds manager Dusty Baker said. "We didn't lose any ground either and it's one less game on the schedule. We've got to feel fortunate it happened, but we've got to win."
Bronson Arroyo (14-10) was hit hard, yielding seven runs in 4 1/3 innings and surrendering a season-high three homers.
"It's a well-balanced lineup, but it's nothing you don't feel you can't pitch to," Arroyo said. "They've been hot, they've play good in this ballpark and we're just not getting it done. They beat me straight up."
The Rockies are red hot at Coors Field, going 15-4 since July 29. Tracy even gave his starters an early exit, pulling most of them in the eighth inning. By the time the game was over, many were showered and gone.
"To give everybody a breather is needed, especially coming into this last month," Young said. "We need everybody going 100 percent."
Votto went 3 for 3 to raise his average to .326. He also drove in a run in the first inning to give him 99 RBIs this season.
With Gonzalez swinging such a hot bat, teams are electing to pitch around him and take their chances with cleanup hitter Tulowitzki.
The strategy backfired Wednesday. After Dexter Fowler led off the third with a single, Arroyo carefully pitched to Gonzalez before walking him.
Tulowitzki jumped all over a hanging curve, hitting a drive to left for his 16th homer.
Then again, pitching to Gonzalez also can be quite hazardous. He hit a three-run drive in Tuesday night's 4-3 victory and is challenging for the NL Triple Crown. He leads in batting average (.340) and RBIs (100), while trailing Albert Pujols by four homers.
Rockies C Mike McKenry made his major league debut as a pinch hitter, flying out to shallow center. ... Rockies RHP Manuel Corpas underwent Tommy John surgery Wednesday. ... Colorado has beaten the Reds nine straight times at Coors Field since Aug. 23, 2008.