In his Diamondbacks debut earlier this week, Trevor Cahill looked less like a former 18-game winner and more like Charlie Sheen's Ricky "Wild Thing" Vaughn.

He'll look to settle down this afternoon and prevent Arizona from getting swept in a three-game series by the Colorado Rockies.

Acquired from the A's this past offseason, Cahill got a no-decision versus San Diego after allowing a run on two hits. He also walked six batters with five strikeouts, though none of the walks he issued came around to score.

"I was just happy to come out with as little damage as possible," Cahill said.

The 24-year-old righty has faced the Rockies just once before, as a rookie with the A's on June 27, 2009. He took a loss in that outing, allowing seven runs and four homers over 3 2/3 frames.

Arizona has lost three of four since a 4-0 start and put together a rain- soaked comeback in Saturday's contest before losing 8-7 on Todd Helton's walk- off homer in the bottom of the ninth inning.

Helton connected on a two-run blast with two outs for his first homer of the season. It capped a game that lasted nearly five hours thanks to a pair of rain delays.

"I didn't think I hit it out. I thought I hit it too high, but I'll take it," Helton said after his club won for the third time in four games.

Tyler Chatwood (1-0) recorded the win by tossing two innings of relief, allowing one run on two hits and one walk with three strikeouts.

Colorado, which played without outfielder Carlos Gonzalez due to strep throat, led 5-1 after four innings before the second delay. Tyler Colvin hit a two-run homer in the second frame and that was followed with a solo blast from Ramon Hernandez.

"Part of baseball," Diamondbacks manager Kirk Gibson mused. "Less than ideal conditions, you could see that Colorado was just trying to get five innings in, they were throwing everybody at us, and we came back and got beat by a good pro, Todd Helton."

After a one-hour, 11-minute rain delay, Miguel Montero began the Diamondbacks' rally by launching Josh Roenicke's pitch over the center-field wall and into the trees at Coors Field for a three-run shot.

One of the players acquired from the Indians last season for Ubaldo Jimenez, left-hander Drew Pomeranz will make his season debut for the Rockies tonight.

Pomeranz made a minor league start on Tuesday in Double-A since the Rockies were not in need of their fifth starter until this afternoon. He threw four scoreless innings, allowing four hits and a walk with four strikeouts.

The 23-year-old went 2-1 with a 5.40 earned run average in four major league starts with the Rockies last season. He faces Arizona for the first time.

The Diamondbacks won seven of their final eight meetings with the Rockies last year and took the season series 13-5. They won six of nine in Colorado.

On this the 65th anniversary of Jackie Robinson breaking the color barrier Major League Baseball is commemorating this special occasion by having all players and on-field personnel once again wear the Hall of Famer's No. 42 in addition to other pregame festivities.