DENVER -- The Colorado Rockies have been able to depend on very little going right during their difficult season. An exception has been Jorge De La Rosa pitching at Coors Field where he has thrived during his career and where he stymied the Cincinnati Reds on Thursday night.

The Rockies opened a 10-game homestand with a 7-3 win over the Reds as De La Rosa (12-8) pitched seven innings and allowed five hits and three runs. Shortstop Charlie Culberson, starting in place of slumping Josh Rutledge, hit a three-run homer in the fifth when the Rockies scored for the fourth straight inning and built a five-run lead.

Coors Field has proven to be a nightmare for plenty of pitchers but not De La Rosa, who has said his breaking pitches move too much on the road but are easier to throw for strikes at Coors Field. He is 8-2 there with a 3.30 ERA this season in 12 starts and 43-14 with a 4.08 ERA at Coors Field in 76 career games (72 starts).

Coming off a 1-5 road trip, the Rockies won for just the second time in eight games, the fourth time in 18 and the seventh time in 28.

Alfredo Simon (12-8) gave up 10 hits and seven runs, five earned, in five innings and was hit hard by the Rockies for the second time this season. While losing two starts against them, Simon has a 11.25 ERA, having allowed 12 runs, 10 earned, and 18 hits in eight innings.

After making the National League All-Star team, Simon has stumbled in the second half, going 0-5 with a 5.46 ERA in six starts.

Culberson's home run gave the Rockies a 7-3 lead. The Reds made it 7-3 with two out in the sixth when Ryan Ludwick hit his seventh homer. It was his seventh career hit and fourth homer in 24 at-bats against De La Rosa. Ludwick had three of Cincinnati's six hits.

The loss was the third straight and fifth in six games for the Reds (60-61), who have scored 13 runs in those five defeats. They fell 6 1/2 games behind in the NL Central and 4 1/2 games back in the wild card chase.

The Rockies capitalized on Simon's throwing error in the fourth to score two unearned runs and go ahead 4-2. He gave up a leadoff single to Culberson and then jumped to grab second baseman DJ LeMahieu's high bouncer. But Simon's low throw to the shortstop side of second base went into center field, allowing Culberson to continue on to third and LeMahieu to take second.

With one out, right fielder Charlie Blackmon grounded to first on Simon's eighth pitch, and Culberson scored. Center fielder Drew Stubbs followed with a run-scoring single up the middle, right past Simon.

Blackmon, Stubbs and first baseman Justin Morneau began the Rockies' third with successive singles. And left fielder Corey Dickerson's sacrifice fly with one out tied the game at two. After the Reds scored twice in the second, Dickerson doubled with one out in the bottom of that inning, moved to third on Simon's wild pitch and scored on Rosario's double.

Catcher Devin Mesoraco led off the second with a walk and scored when left fielder Ryan Ludwick followed with a double, the 200th of his career. He took third on a groundout and scored on a two-out single by No. 8 hitter Zack Cosart, who came to bat hitting .224 overall and .188 (18-for-96) with runners in scoring position.

NOTES: Reds RHP Homer Bailey will be placed on the disabled list with a strained right flexor mass tendon near his forearm and not make his scheduled start Saturday. The Reds played a man short of the 25-player limit as Reds manager Bryan Price said roster moves and Saturday's starter will be announced Friday. ... Rockies SS Troy Tulowitzki will undergo surgery on the labrum in his left hip on Friday in Vail, Colo., and miss the balance of the season. ... Rockies RF Michael Cuddyer (fractured left shoulder socket) is scheduled to play his final rehab game Thursday for Double-A Tulsa, return to Denver on Friday and, if all goes well, be activated Saturday. ... Reds 2B Brandon Phillips (torn ligament left thumb) and RHP Logan Ondrusek (right shoulder strain) are scheduled to begin rehab assignments Friday at Triple-A Louisville. ... Reds RF Jay Bruce, who was a late scratch Wednesday because of illness, was in the lineup Thursday.