CINCINNATI -- Robert Stephenson learned Monday night that he was being pressed into service when scheduled starter Alfredo Simon couldn't go because of biceps tendinitis.

"I had plenty of time to prepare," he said. "I took it like a regular start."

Stephenson calmly gathered his things and drove to Great American Ball Park, where hours later he just as confidently dominated a formidable Colorado Rockies lineup.

Stephenson, making his second career start, allowed one run in seven innings and Brandon Phillips fell a homer shy of the cycle as the Cincinnati Reds defeated the Colorado Rockies 4-3 on Tuesday night.

Stephenson (2-0) labored only briefly in the second inning but rolled after that, giving up just three hits with two walks and three strikeouts.

After making his debut in Cincinnati's third game this season, Stephenson became the first Reds pitcher to win his first two career starts since Larry Luebbers in 1993.

"He was terrific," Reds manager Bryan Price said. "He was able to build some confidence against a really good lineup. We were essentially down to a five-man bullpen. It helped to have him pitch deeper into the game."

Phillips singled, doubled and tripled in his first three at-bats before he singled again in the ninth to finish 4-for-4.

Cincinnati stole five bases, all in the second inning against Rockies starter Jorge De La Rosa.

"When he wasn't slide-stepping, his times were deliberate," Price said. "We don't want to be a station-to-station team here, but we took advantage of that."

De La Rosa (1-2) lasted just two innings and took the loss for Colorado (8-6), which got six scoreless innings of relief, including four by Chris Rusin, who gave up two hits.

Yet again, the bullpen made things interesting for Cincinnati (7-7) when struggling closer J.J. Hoover, working in a non-save situation, allowed a two-run homer by Mark Reynolds with two outs in the ninth, but got the final out.

Stephenson gave up three earned runs in five innings in his major league debut on April 7 against the Philadelphia Phillies. He was even more composed Tuesday, with a fastball that reached 96 mph while effectively mixing in his changeup.

"The first time out, I was just trying to go out there and throw strikes," Stephenson said. "Little bit warmer weather (tonight), my arm did feel really good. I was able to let it go a little bit more tonight. It eased the nerves knowing I'd been here before and I belong here."

Stephenson retired the first five batters he faced. But with two outs in the second, Reynolds doubled, advanced to third on a balk, then scored on Ben Paulsen's broken-bat single to center, putting the Rockies up 1-0.

Pitching coach Mark Riggins made one visit to the mound in the second. After that, Stephenson was in control.

"There was no reason I couldn't get guys out if I just went right after them," Stephenson said of Riggins' message.

As for De La Rosa, the wheels came off as the Reds ran wild in the bottom of the second.

Cincinnati stole five bases in the inning, two by Jay Bruce, their most in one inning since at least the 1920s, according to the Elias Sports Bureau.

"He was having a hard time throwing strikes and getting outs, so all of his focus went to getting the hitters out and they took advantage on the bases," manager Walt Weiss said.

Of the five steals, Bruce said, "It's a rare thing, like an eclipse."

Cincinnati made the Rockies pay.

Billy Hamilton's two-run double and an RBI single by Zack Cozart that extended his hitting streak to eight staked the Reds to a 4-1 lead.

After allowing a double and a walk to begin the third, De La Rosa was lifted for Rusin. De La Rosa was charged with four runs in two-plus innings.

"I lost my concentration," De La Rosa said. "I wasn't paying attention to the runners. I have to do a better job than that."

As for Stephenson, he's likely headed back to Triple-A for a bit more seasoning, although he could rejoin the club if Simon's injury is more serious. But clearly the 23-year old is a major component of the Reds' rebuilding efforts.

"Whatever they want me to do," Stephenson said. "Every time I come back here I just want to be able to come out here and help the team win."

NOTES: RHP Robert Stephenson was recalled from Triple-A Louisville to make his second career start in Simon's place and RHP Jumbo Diaz was optioned to Triple-A to clear room. ... Rockies 2B DJ LeMahieu returned to action after missing two games with groin tightness. ... Reds C Devin Mesoraco and 3B Eugenio Suarez were back in the lineup after a day off.