DENVER -- The Colorado Rockies have had very little go right during their difficult season. An exception is when Jorge De La Rosa pitches at Coors Field.

The Rockies opened a 10-game homestand Thursday night with a 7-3 win over the Cincinnati 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 inning when the Rockies scored for the fourth straight inning and built a five-run lead.

Coors Field has proved 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 command at Coors Field. He is 8-2 at home 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).

"His changeup again was his go-to (pitch)," Rockies manager Walt Weiss said. "Cutter was good. That's what we've seen a lot in the last couple of years from Jorge, especially here."

Weiss said De La Rosa tweaked his Achilles tendon running to first base in the second inning after giving up two runs in the top of that inning but allowed just three hits and one run during the remainder of his start.

"We were on edge there for a little while," Weiss said. "He got through seven and that was huge for us. If your starter gets through seven, the game tends to fall in place for you."

De La Rosa has made a career-high 10 consecutive starts of at least six innings.

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.

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

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.

"He made some mistakes and they hit it hard," Reds manager Bryan Price said. "Threw a few good splits. Didn't really have much of a curveball, and his cutter wasn't what we've grown accustomed to.

"He pitched ahead better today. He was more aggressive in the count, but they were very, very comfortable at the plate and they hit a lot of balls hard and that's a bad combination."

Simon made a throwing error on a potential double play ball, leading to two unearned runs in the fourth inning that put the Rockies ahead 4-2. And Culberson hit his third homer of the season an inning later and his second three-run shot of the season.

After going 12-3 with a 2.70 ERA in 18 starts and making the NL All-Star team, Simon has stumbled in the second half, going 0-5 with a 5.46 ERA in six starts.

"They're not missing his fastball," Price said. "They're not hitting it into the ground. They're able to elevate it and get it into the outfield. ... He hasn't located very well. He hasn't been able to blend his pitches consistently in the zone."

Culberson's home run gave the Rockies a 7-2 lead. The Reds made it 7-3 with two outs in the sixth inning when Ryan Ludwick, who was 0-for-13 entering the game, connected on a 3-2 changeup for his seventh homer of the season. It was his seventh career hit and fourth homer in 24 at-bats against De La Rosa.

"Maybe he's made some mistakes to me that he hasn't made to other guys," said Ludwick, who had three of Cincinnati's six hits. "He's been around this league for a long time because he is good at what he does. Today, I just happened to think along with him. They threw a cutter up and in, so I was sitting dead change. If he throws a heater, and it catches the corner I'm done. Lucky guess."

NOTES: Rockies RF Carlos Gonzalez (left knee tendinitis) will undergo season-ending surgery Monday in Frisco, Colo. ... 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) was 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.