DENVER -- The blasts returned to Coors Field long before the fireworks.

In a throwback to the pre-humidor days, Colorado homered six times and beat the Florida Marlins 18-17 on Friday night after trailing by nine runs in the biggest comeback in Rockies history.

Chris Iannetta singled home the winning run off Kevin Gregg in the ninth inning.

Garrett Atkins, who had a career-best five hits, drove in the tying run off Gregg (6-4), who blew his second save in 24 hours. After Hanley Ramirez's error on a potential double-play groundball loaded the bases, Iannetta singled to left through a drawn-in infield.

"When you're in a game like that you never know what's going to happen," Iannetta said. "You know you have a chance no matter what. We just kept battling and kept coming."

The last time a team came back to win from nine down was Aug. 23, 2006, when Cleveland rallied for a 15-13 victory at Kansas City, according to the Elias Sports Bureau.

In the highest-scoring game at Coors Field since the humidor was introduced in 2002, bringing some sanity to mile-high baseball, the Rockies and Marlins combined for 35 runs on 43 hits, 21 of them for extra bases with eight home runs.

"It was a fun game to be hitting," Atkins said. "It wasn't a fun game to be playing defense."

The last time two teams combined for this many runs was May 19, 1999, also at Coors Field, when the Cincinnati Reds roughed up the Rockies 24-12.

Colorado scored in every inning but the eighth, yet trailed until Atkins' tying single in the ninth. Taylor Buchholz (3-2) threw one inning for the win, Colorado's fourth straight.

The Rockies hit a half-dozen homers, two each by Ryan Spilborghs and Matt Holliday, who had his third career grand slam. Atkins and Iannetta also went deep for Colorado, which hadn't had this many long balls in a game since 1999.

"If people came for the fireworks, they got more than the postgame fireworks," Holliday said. "They got their money's worth. Almost 40 runs, 40 hits."

Florida set season highs in runs and hits (22). Cody Ross drove in five runs for the Marlins, who had never blown a lead this big before. Jorge Cantu scored four times and Mike Jacobs went 4 for 4 and reached base all six times in a losing cause.

Until Gregg blew his second straight save, left-hander Scott Olsen was in line for the win despite allowing nine runs (eight earned) and 11 hits -- including three homers -- in five innings.

The Rockies scored 12 straight runs via the long ball after falling behind 13-4 in the fourth inning.

"That was one of those throwback games from back in the day: the last team to hit," Rockies manager Clint Hurdle said. "This was by far the most fun I've had watching our team swinging the bat in a long time, if not ever. You go up and down the lineup there's a whole host of stars."