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While one of their top young sluggers recovers from strep throat, more than a few Colorado Rockies fans may have hoarse throats after the first two games of their series against the Arizona Diamondbacks.

That's because grizzled veteran Todd Helton is showing he's got plenty of pop left in his bat.

Coming off a pair of dramatic wins, Helton and the Rockies go for a three-game sweep of the NL West rival Diamondbacks on Sunday at Coors Field.

Colorado (4-4) took the series opener 7-6 on Friday night, scoring the deciding run when Helton doubled home Carlos Gonzalez with two outs in the bottom of the eighth inning. Gonzalez missed Saturday's game due to strep throat but Helton helped the Rockies overcome his absence, launching a two-run homer just inside the right-field foul pole off Arizona closer J.J. Putz with two outs in the bottom of the ninth to give Colorado an 8-7 victory.

"There will be days when I don't get the big hit," Helton said. "So I don't put too much into it. I treat it like any other at-bat."

While Gonzalez and Troy Tulowitzki may post the gaudiest numbers these days, the Rockies' 16-year veteran first baseman is proving vital to their early success. In the club's four wins, Helton has gone 8 for 19 (.421) with three doubles and seven RBIs. He's 0 for 9 in Colorado's four losses.

The Rockies' entire offense has been similarly feast or famine. Colorado is averaging 9.3 runs and batting .353 in its victories, while it's totaled seven runs and hit .177 in the defeats.

Gonzalez's status is uncertain for the series finale, but Tyler Colvin did an admirable job filling in as the starting left fielder Saturday, going 2 for 4 with a two-run homer.

Highly touted left-hander Drew Pomeranz will make his season debut Sunday for the Rockies. Acquired last summer in the trade that sent Ubaldo Jimenez to Cleveland, Pomeranz went 2-1 with a 5.40 ERA in four September starts. This season, Colorado is expecting bigger things from the 23-year-old rookie.

"There's more life to his pitches than when he was competing for us last September," manager Jim Tracy told the Rockies' official website. "There's no getting around the fact he had a tremendous spring training."

Pomeranz has never faced the Diamondbacks, and scheduled Arizona starter Trevor Cahill may wish he'd never faced the Rockies before Sunday. The right-hander allowed seven runs and eight hits -- four homers -- in 3 2/3 innings against Colorado in an 11-9 home loss for Oakland on June 27, 2009. If there's a silver lining from that outing for Cahill, it's that none of the players who homered off him in that contest are still on the Rockies.

Cahill, whom the Diamondbacks obtained from the Athletics in a five-player offseason trade, walked six over six innings Tuesday in his debut for his new team, but limited San Diego to one run and two hits. Arizona went on to win 4-2 in 11 innings.

The defending West champion Diamondbacks (5-3) are trying to avoid being swept by any division rival for the first time since dropping three straight at San Francisco last May 10-12, and their first sweep at Coors since Sept. 10-12, 2010.