DENVER -- The Cubs came back to Coors Field still hungry for success Saturday night, their appetite merely whetted by Friday's win over the Rockies. But in a pitchers' duel, when defense was at a premium, it was the Rockies who feasted on a 4-2 victory.

Glendon Rusch (5-6) pitched well, lasting six innings and yielding only two earned runs, but a suspect defense and an inefficient offense proved to be a one-two punch he couldn't counter.

Rusch suffered through a challenging first inning, as the Rockies took advantage of three hits, a walk and an error to take a two-run lead. The first run wasn't so hard to swallow: a leadoff infield hit, a sacrifice and an RBI single from Todd Helton.

But the second came on a two-out, bases-loaded grounder to second from Todd Greene that Todd Walker bobbled, allowing Helton to score.

"It makes it tough when you give them runs," said manager Dusty Baker. "We didn't play good defense tonight, and that's really kind of been hurting us most of the year."

Rusch was at his most vulnerable in the third inning, when the Rockies scored again on consecutive singles from Matt Holliday, Garrett Atkins and Dustan Mohr, but even Mohr's RBI single came on a questionable defensive play from left fielder Matt Lawton, who lunged forward for the ball, only to see it skip off his glove as Holliday scored the Rockies' third run.

"I definitely should have caught it," said Lawton. "I don't think I had to dive, but I had to try to get underneath the lights. The ball was in the lights, so I tried to dive to get underneath them. Once I got underneath the lights, I saw the ball really well. It just hit off my glove and it cost us a run."

Rusch gave up only one hit in the other four innings he pitched, a quality start in any park, but a heart-breaking loss in the offensive-oriented Coors Field.

"On a night when [Rockies starter Aaron] Cook pitches as well as he does, it doesn't look as strong as it could have been," said Rusch of his performance. "On a regular night at this ballpark, usually you're pretty happy if you get yourself through six and give your team a chance to win. But as dominant as he was tonight, we had to play catch-up all night."

The Cubs were stymied by Cook (2-1), who scattered seven hits over seven innings, taking advantage of sterling defensive work behind him to thwart any would-be rallies from the Cubs.

"He has probably one of the better sinkers in the league," said Baker. "You can see by the number of ground balls [14 of 21 outs] that he threw. He threw almost all sinkers. To me, that's still one of the best pitches in baseball, especially when you have a good infield defense."

The combination of a ground-ball pitcher and an infield rising to the occasion kept Chicago from ever building momentum at the plate. The Cubs had men in scoring position in each of the first four innings, largely as a result of leadoff hits in three of those four innings, but they couldn't finish the job.

"We hit a lot of balls right at guys," said Lawton. "Too bad it had to happen at a time when we're trying to make up some ground and we're playing really good baseball. We had a lot of great opportunities, we just didn't get it done tonight."

The Cubs finally broke through in the seventh, when Neifi Perez doubled to right-center and pinch-hitter Todd Hollandsworth drove him home with a single up the middle.

With Cook out after seven, the Cubs battled back in the eighth, staging a one-out rally against reliever Mike DeJean. Derrek Lee got it started with a double to the left-field corner. Aramis Ramirez drove him home with a single to left, and with another single from Jeromy Burnitz and a walk to Michael Barrett, the bases were jammed for Perez.

Perez skied a fly to short, giving Corey Patterson the chance to turn the game around, but Patterson grounded to second on the first pitch, capping a night of missed chances.

"I'll take those at-bats any day," said Patterson. "It's really not about me, it's the team collectively, and we lost. It's a tough game. We fought back right there. I don't think there's anything for us to hang our heads about, because we played well."

With the game still tight at 3-2, the previously impenetrable Kerry Wood entered the game in the bottom of the eighth. Wood had a perfect 0.00 ERA for his August in the bullpen, allowing just one hit in seven appearances. But after inducing Atkins to fly to right, Mohr took Wood's first offering, a 97-mph fastball, and deposited it 444 feet into the center-field seats, giving the Rockies a two-run cushion.

"You have to go up there looking for a fastball," said Mohr. "He throws too hard to look for anything else."

Brian Fuentes came in to pitch the ninth for the Rockies, striking out pinch-hitter Nomar Garciaparra before yielding a two-out bloop single to Walker, setting up a showdown with Lee at the plate, representing the tying run.

"That's about as good as it gets in baseball, when you get your closer up against somebody in the running for MVP in front of a big house," said Rockies manager Clint Hurdle. "Quite a number of pitches were thrown and both guys were battling. That's top-shelf stuff."

Fuentes won the battle on the 10th pitch, inducing Lee to ground out to Helton at first and earning his 21st save.