Chris Capuano is Dodgers’ surprise ace

When the Dodgers signed Chris Capuano over the winter, their expectations for him were modest.

He was supposed to be their fifth starter. If not for Ted Lilly starting the season on the disabled list, his first turn in the rotation would have been skipped.

But something unexpected has happened. Capuano is pitching like an ace.

The 33-year-old left-hander was again spectacular in the Dodgers’ 7-3 victory over the Colorado Rockies on Tuesday night, limiting the visitors to a run and four hits over seven innings.

Capuano improved his record to 5-0 and dropped his earned-run average to 2.06. The solo home run he served up to Michael Cuddyer in the seventh inning ended a 242/3-scoreless-innings streak.

“I’m feeling good out there,” Capuano said. “I’m making some good pitches. I’m able to keep my focus small and make pitches one at a time.”

A bulk of the run support he received came from another better-than-expected free agent addition, Mark Ellis, who sent an 80-mph fastball by 49-year-old Rockies starter Jamie Moyer over the left-field wall in the first inning.

A stabilizing presence in the middle of an infield that includes the unseasoned Dee Gordon, Ellis added a two-run double in the Dodgers’ three-run fifth inning. He finished the night with three runs batted in.

Like Ellis, Juan Uribe hit his first home run of the season, belting an eighth-inning solo home run that counted as the Dodgers’ final run.

Andre Ethier drove in two runs to increase his National League-leading RBI total to 32. Ethier was three for four with a home run and a double. The home run was his seventh.

Now 21-11, the Dodgers have a six-game lead over the second-place San Francisco Giants in the NL West, their widest margin of the season.

Of course, fast starts can be deceiving. Capuano knows that better than anyone else.

The only other time he started a season 5-0 was in 2007 with the Milwaukee Brewers. He didn’t win another game the rest of the season and finished the year 5-12.

At the end of that year, he underwent reconstructive elbow surgery.

“I’ve gone through so much since then,” Capuano said.

He missed the entire 2008 season. He pitched in six minor league games the following year.

The former All-Star pitched in 24 games for the Brewers in 2010, but started only nine times. He made 31 starts last season with the New York Mets and was 11-12 with a 4.55 ERA.

“Early in the year last year, I had a little trouble getting through the fourth, fifth, sixth inning,” he said. “I feel a lot better than last year from that standpoint. I feel like I’m able to feel stronger later in the game.”

Of his past elbow problems, Capuano said, “It’s not a thought for me.”

Drawing on his experience as an opposing hitting coach preparing players to face Capuano, Manager Don Mattingly said he knew the left-hander had these qualities in him.

“He’s a tough guy to scout,” Mattingly said. “He has so many pitches. He’s hard to prepare for.”

However, not everything went well for the Dodgers. Javy Guerra entered the game in the eighth inning, making his first appearance since he lost his job as closer to Kenley Jansen. Guerra was unable to get out of the inning. He recorded two outs but gave up a hit and a walk.

dylan.hernandez@latimes.com