LeMahieu said the Rockies' familiarity with Volquez was a big factor in their offensive burst.
"I don't think it's anything he's doing," LeMahieu said. "It's just that we've seen him so many times, we kind of know what he's going to do. He threw me a breaking ball (on the homer). He hung it a little bit and I was trying to be aggressive, too, but he hung it. I'm sure he'd want that pitch back."
The Rockies added three more runs in the fifth. Todd Helton and Arenado had successive singles. After Charlie Blackmon hit into force play, Volquez walked LeMahieu to load the bases, ending his night.
Chacin greeted Sean O'Sullivan with a deep fly to right that scored Arenado, and Fowler followed with a sharp single to right to drive in two more runs for an 8-0 lead.
Decker broke up Chacin's shutout bid with two outs in the seventh when he homered for his first major league hit. Decker's drive reached the seats in right center.
After the Rockies came off the rain delay to score six runs in the eighth, helped by the Padres' fourth error of the game on a dropped throw by first baseman Alonso, Gyorko connected off Jeff Francis for his 11th homer.
NOTES: The Rockies' previous high for runs in a game was 12, which was achieved twice. ... Padres OF Kyle Blanks, on the 15-day disabled list since mid-July with a left Achilles' injury, is set to begin running again later this week. Manager Bud Black said before the game he's on track to be activated soon. ... Rockies OF Michael Cuddyer missed a second consecutive game because of an illness. ... Padres LHP Eric Stults (8-10) is slated to pitch the second game of the set against Jeff Manship (0-1), who was recalled a week ago from the club's Triple-A affiliate in Colorado Springs.
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