DENVER(AP) It looks like 2007 all over again at Coors Field.

Todd Helton hit a two-run homer with one out in the ninth inning and the Colorado Rockies won their fourth straight game, beating the Pittsburgh Pirates 9-7 Saturday night.

The Rockies have won 15 of 16 overall. Two years ago, the Rockies suddenly went on a similar run to reach the World Series.

''That's an incredible win right there, and incredible win,'' manager Jim Tracy said. ''We obviously had to do some very special things to win.''

''There is a belief in this clubhouse we show up every day expecting to win,'' he said.

The Rockies improved to 17-5 since Tracy took over for Clint Hurdle on May 29.

''We're doing some great things,'' Helton said. ''We're playing well, pitching deep into the game and getting hits.''

Colorado's Chris Iannetta tied it at 7 with three-run homer in the eighth. Ian Stewart came within a single of hitting for the cycle and drove in three runs for the Rockies.

Huston Street (2-1) pitched a scoreless ninth for the victory. Colorado's Jason Hammel allowed five runs on eight hits in six-plus innings.

Andrew McCutchen hit a bases-loaded triple, Nyjer Morgan matched a career high with four hits and Brandon Moss added two RBIs on three hits for the Pirates, who have lost six straight at Coors Field.

''This was a tough loss, but we've already had a lot of tough losses this year,'' Pittsburgh manager John Russell said. ''We swung the bats better tonight, but unfortunately our bullpen couldn't hold them.''

''Those things happen when you're going up against a hot team,'' he said.

Trailing 7-4 in the eighth, John Grabow walked Brad Hawpe and gave up a two-out single to Carlos Gonzalez before Iannetta followed with a home run to center.

''I've not managed a club that had an eight hole hitter in the lineup that can hit a baseball that far,'' Tracy said of Iannetta. ''I've not managed a club that had an offense that's performing and as deep as this one is when you have an offense like that it gives you an opportunity to come back in a situation like we were in tonight.''

Pinch-hitter Seth Smith singled off Jesse Chavez (0-3) with one out before Helton's drive into the Pirates' bullpen in right center field.

''He threw me a fastball, the same pitch he threw the pitch before,'' Helton said.

Chavez acknowledged as much.

''I tried to come back inside with a fastball,'' Chavez said. ''But I got it up and like the good hitter he is, he hit it out.''

The Pirates took a 6-4 lead with a four-run seventh inning highlighted by McCutchen's three-run triple. Moss added an RBI double in the eighth.

The Rockies led 4-2 after Stewart's two-run homer to straightaway center off Sean Burnett with one out and Tulowitzki aboard in the sixth.

Pittsburgh went ahead 2-1 in the third on Freddy Sanchez 's RBI double into the gap in right after Stewart's RBI double. He added a triple in the next inning, scoring on an RBI single by Carlos Gonzalez .

''I think that you look at significant situations that allowed the heroics of Chris and Todd,'' Tracy said. ''It comes down to this is a game that's won by the Colorado Rockies baseball team.''

NOTES: The walkoff home run was the first by Colorado this year. ... Rockies setup man Manny Corpas was placed on the 15-day disabled list due to inflammation caused by a floating bone chip his right elbow a day after receiving a cortisone shot and an MRI exam. ... Rockies LHP Greg Smith will make a rehab start on Tuesday for Double-A Tulsa. ... Morgan caught a foul ball while sitting on top of the wall along the left-field line in the third inning. ... Grabow moved into 10th place and third among all left-handers for the Pirates with his 376th appearance.