A shaky pitching staff and an inconsistent lineup have both hurt the Colorado Rockies as the NL champs are off to one of baseball's most disappointing starts in 2008.

Having to face the Arizona Diamondbacks so often also hasn't helped.

The Diamondbacks, swept by the Rockies in last season's NLCS but sporting the league's best record in 2008, look for their seventh win in eight tries against their NL West rivals as the teams continue a three-game set on Wednesday at Chase Field.

Arizona (24-15) won the NL West last season, but dropped four straight to Colorado in the playoffs, sending the Rockies to the World Series for the first time and sending the Diamondbacks home for the winter.

Arizona - off to one of baseball's best starts in 2008 - has relied on its power and its impressive pitching staff as the keys to its hot start.

Colorado (15-24) has gotten an up-close look at what's made the Diamondbacks so successful. In seven games against the Rockies, Arizona has hit 12 homers and scored 51 runs while batting .323.

The Diamondbacks have six of their 18 NL West wins against Colorado.

"It's good to be able to play well against our division," right fielder Justin Upton said. "We've seen these guys quite a few times, so we feel comfortable."

And aside from a 13-run outburst that accounted for Colorado's only win in those first seven games, Diamondback pitchers have gone 6-0 with a 2.13 ERA against the Rockies.

Arizona's bats delivered again on Tuesday night, scoring six runs in the first two innings en route to an 8-4 win.

"It felt good with the team coming out early and putting up some runs," said shortstop Stephen Drew, who hit his fifth homer.

The Diamondbacks will send a pitcher to the hill on Wednesday who's equally capable of helping his team with his bat. Micah Owings (4-1, 4.33 ERA) is batting .417 with a homer and three RBIs, and has been used six times as a pinch hitter.

Owings hasn't picked up a victory since winning his first four starts of the season, but he pitched well in his last outing. He gave up three runs on four hits over seven innings to Philadelphia last Wednesday, striking out nine, but the Phillies rallied against Arizona's bullpen for a 5-4 win.

Owings' best start of the season came at Colorado on April 4. He gave up one run on two hits in 6 2-3 innings, striking out nine in Arizona's 8-1 win.

After winning three straight, the Rockies have lost three in a row and struggled offensively. Colorado has scored only seven runs in the three losses, going 3-for-23 with runners in scoring position.

"We obviously haven't put anything together," left fielder Matt Holliday said. "That's been the challenge, trying to match scoring four or five runs and having good pitching outings on the same day."

Holliday certainly can't be blamed for the team's offensive issues. He's hitting .400 (14-for-35) over his last nine games with two homers and five RBIs. He's struck out in all three career at-bats against Owings, however.

Jorge De La Rosa (1-1, 10.24) will get a third start for Colorado after his second outing went much better than the first. He gave up nine runs in his debut against Los Angeles on May 3, then settled down against St. Louis on Thursday, allowing two runs over 5 2-3 innings in a 9-3 win.

"Everything was different," said De La Rosa. "I felt much better. I mixed my pitches very good."