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DENVER -- A typically reserved Todd Helton lost control of his emotions, throwing his hands in the air and jumping around as he circled the bases.

Leave it to a walk-off homer to bring out the kid in a veteran player.

Helton hit a two-out, two-run homer off closer J.J. Putz in the bottom of the ninth inning and the Colorado Rockies rallied for an 8-7 win over the Arizona Diamondbacks on a rain-soaked Saturday night.

"I'll take it," Helton said after the game, getting his emotions back in check.

He didn't think it was gone, though.

Too high, he figured.

And no way does the ball cut through the thick raindrops that were falling.

But it wasn't too high, and the downpour only enhanced the moment.

For the second straight evening, Helton stepped into the role of hero for the Rockies.

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

Only, this wasn't any other at-bat.

He sent a fastball from Putz high into the rainy-night sky as Justin Upton retreated to the warning track. But there was nothing Upton could do but stare -- the ball was gone by quite a bit, and it stayed just fair down the right-field line.

As for his emotional outburst, well, Helton wanted to apologize. He usually doesn't get that crazy. He was just swept up in the moment, as were his teammates who mobbed him at home plate.

"Walk-off home runs are always nice," Helton said.

He should know -- he's had seven in his career, but this was his first in nearly three years.

"It was fun," he said.

Not for Putz, who would love to have that pitch back.

"Tried to sneak one in," explained Putz, who had his team-record streak of 28 straight saves halted. "I got it in but it was up and he's been doing that for a long time. He put a good swing on it and it got out."

Tyler Chatwood (1-0) pitched two innings and gave up a run to earn the win in relief.

The Diamondbacks were trailing 5-1 when the game was halted by a relentless downpour after four innings. But the 71-minute break energized their bats and they came out of the clubhouse swinging.

Miguel Montero hit a three-run homer and pinch-hitter Paul Goldschmidt broke a tie with a sacrifice fly in the seventh.

The lead wouldn't last as Putz (0-1) hit Marco Scutaro with a pitch to start the ninth inning, but got pinch-hitter Jason Giambi to pop up and then struck out Troy Tulowitzki.

That set the stage for Helton.

"I was just trying to get a grip on the bat at that point. It was raining pretty hard," Helton said. "I knew it wasn't going foul. I didn't know if it had enough distance."

It did, setting off a raucous celebration for the fans who braved the elements until the end.

On this dreary night in the Mile High City, the grounds crew kept shoveling layers of diamond dust on the soaked infield to dry it out, but that hardly helped. The persistent rain made every play an adventure.

So slick was the field that smooth-fielding shortstop Tulowitzki made two throwing errors -- in one inning.

Later, left fielder Gerardo Parra slipped while chasing down an RBI double by Eric Young Jr., which made it a 7-6 game.

All this after hard-luck starter Jhoulys Chacin departed.

These days, Chacin can't win even when the hard-throwing righty is, well, winning.

He was rolling along in the drizzle as he methodically set down the Diamondbacks with a more aggressive approach on the mound. But just as he was about to duck out of the dugout for the fifth inning, the umpires signaled for the tarp.

With that, his night was finished.

Chacin had his good stuff, too, the kind of movement on his pitches that has led manager Jim Tracy to proclaim him an ace in the making. He scattered four hits and gave up one run over four innings, but is still searching for his first win since Aug. 28.

It was definitely a step in the right direction.

"If we win, I'm happy," Chacin said.

Chacin also helped himself at the plate, driving in a run on a grounder off counterpart Josh Collmenter, who was taken off the hook for a second straight outing.

Collmenter gave up six runs -- five earned -- in three innings against the Giants, only to see his team rally back in that game, too.

In these this damp and cool conditions, Collmenter's cutter did anything but cut, especially in the second inning as the Rockies hit back-to-back homers.

Tyler Colvin lined a two-run shot to right. Four pitches later, Ramon Hernandez crushed another Collmenter cutter for a solo drive to straightaway center.

Colvin started in left with Carlos Gonzalez taking a sick day due to strep throat.

Game notes

The start was delayed 16 minutes by a steady rain. ... Before the game, the Rockies reinstated Charlie Blackmon (turf toe) from the 15-day disabled list and optioned the outfielder to Triple-A Colorado Springs.