Already up 2-0 thanks to an offense that awakened quickly after a two-run effort in Monday's loss, the Cardinals ended Colorado starter Juan Nicasio's night in the third.
The rally started with a double from the former Rockie Holliday, who scored when Yadier Molina smoked his 40th double of the year off the right-field wall. Matt Adams hit an RBI single and David Freese followed with a walk before Daniel Descalso hit a line-hugging triple into the right-field corner to put St. Louis ahead, 6-0.
"Everybody's up there battling pitch-to-pitch and just trying to get it from the next guy, get on base and get the next guy up there, knowing that the next guy's going to have a good at-bat too," said Descalso, who went 2-for-5. "So we put together good at-bats in bunches. That's when we have those big innings."
But even then, the Cardinals kept the metal pressed firmly to the floor. Matt Carpenter's RBI single finally chased Nicasio and Holliday's second hit of the inning -- an RBI single to right -- made it 8-0 before Carlos Beltran's groundout brought the inning to a merciful end.
Nicasio (8-8) gave up eight hits and eight runs -- matching a season high -- striking out two and walking three.
"I didn't have control of my fastball, so I had trouble," Nicasio said. "When I can't throw my fastball for a strike down in the zone, it's hard for me."
The Cardinals entered Tuesday's game in a tie with the Pirates atop the division, but Pittsburgh lost to San Diego, 5-2, for its second straight loss. The Reds routed Houston, 10-0, to remain 2 1/2 games back and keep things crowded at the top.
Holliday pushed his former club even further out of reach with a two-run home run into the Rockies' bullpen in the fifth. It was his 20th home run, the eighth straight year he's reached that mark, and Holliday is hitting .417 with seven homers at Coors Field since joining the Cardinals in 2009.
His familiarity with Coors Field has also helped Holliday in the park's expansive outfield, as he made a two-out, leaping grab against the left-field fence to rob his friend and former teammate Todd Helton of a hit with runners on the corners in the first.
"Yeah, he wasn't thrilled about that," Holliday said.
The 10 early runs provided a large cushion for Joe Kelly (9-4), who tossed five shutout innings, giving up only three singles and two walks as he earned his sixth win in seven starts.
But the outing was cut short by right calf tightness. Though Kelly wanted to keep pitching, Cardinals manager Mike Matheny didn't want to push the envelope on a pitcher who could be a crucial piece of his postseason rotation.
"We went out and talked to him, and he said he feels it and felt it all game, but nothing different," Matheny said. "Once he got through the fifth, having a reasonable pitch count to get him out, try and save it a little bit."
In his career debut at Coors Field, Kelly, who threw 78 pitches, didn't look like a man worried by the park's notorious reputation as a difficult place to pitch, and he now has a 1.94 ERA since June 1, second lowest in the Majors. With a big lead, he attacked hitters with a low fastball to draw ground balls and mixed in a curveball.
"I've heard stories and people have told me stuff, but that's the last thing that goes through my head when I get out there," Kelly said about the ballpark. "Just me and [catcher Yadier Molina] when it comes gametime."
Molina drove in St. Louis' first run when he chopped a single to center to score Jon Jay, who reached on a walk. Carpenter made it 2-0 in the second with a single to score Descalso.
Reliever Carlos Martinez threw a scoreless sixth, but he allowed the Rockies to score four runs in the seventh. Pinch-hitter Charlie Culberson slid into third after backup right fielder Shane Robinson bobbled his single, driving home the Rockies' first two runs.
DJ LeMahieu then lined a ball off Martinez's glove when Adams couldn't get his foot on first base to beat out the runner for the final out, scoring Culberson before Michael Cuddyer dropped an RBI single to right.
Carpenter crossed home on a wild pitch in the ninth for the Cardinals' final run, a footnote in a game rich with offensive fireworks. But to Matheny, that play illustrated something else -- that even with a six-run lead and half an inning remaining, they refused to let even the slightest opportunities slip away.
"That's a philosophy, that's just a mentality and [Molina's] the same way, really grinding and grinding and never wanting to give one up," he said. "Those are the kind of ideas or philosophies that turn into a real big season."