Yes, his legs.
Peavy, who fanned a season-high 13 over eight scoreless innings to tie the Major League high for strikeouts this season, didn't factor in the decision, though he helped put the Padres (53-83) in position to win when he raced all the way from first to score on Luis Rodriguez's RBI double in the fifth inning.
"No doubt, Jake goes all out, plays 100 percent," said San Diego third-base coach Glenn Hoffman. "He was already full-bore coming to third base. When that ball fell in, it made my decision to wave him home a lot easier."
It was Rodriguez who came up with the game-winner, sitting back on a curveball in the bottom of the ninth inning, as Will Venable raced home from third base with the winning run a half inning after closer Trevor Hoffman lost the lead.
"I had faith we were going to win it in the bottom of the ninth," Rodriguez said.
As for Peavy, he was equally pleased with his ability to get a head start on Rodriguez's hit in the fifth inning as he was any of his 13 strikeouts or the eight scoreless innings as he pumped fastball after fastball past the Rockies (64-74).
"Right from the get-go, you could tell the fastball had life to it," San Diego manager Bud Black said. "The command was there. I thought he pitched with his fastball as good as he has all year."
His bat and legs weren't too shabby, either.
In the fifth inning and with Colorado pitcher Jeff Francis looking every bit a good as he was a year ago when he won 17 games, it appeared that one run might actually be plenty to decide this game. It nearly was.
With one out, Peavy singled softly to center field off Francis. After leadoff hitter Brian Giles, who had two hits, popped out to Troy Tulowitzki at shortstop, Rodriguez came to the plate. It was about at that point when Peavy decided he was going to try and steal a base against Francis, a risky move for a baserunner against a left-handed pitcher.
Instead, the inning nearly ended with Peavy swimming in a sea of dirt, as Francis threw over to first base and nearly nabbed Peavy too far off the base.
"I was really close to getting picked off," Peavy said.
Undaunted, Peavy took off for second base on a 1-2 count on Rodriguez. He didn't slow down until he crossed the plate, as Rodriguez's double to the gap in right-center was deep enough.
"I trust these guys and their baseball instincts," Black said when asked if Peavy had a green light to run in that situation. "It is, at times, risky. At times the reward is high. It was a good play."
And an important one, especially when the Rockies tied the game in the top of the ninth inning, when pinch-hitter Chris Iannetta bounced a two-out single up the middle to score Brad Hawpe, who singled with one out against Hoffman (3-6).
That run took Peavy out of the running for his 10th victory of the season. He lowered his ERA to 2.69, a shade higher than the 2.54 ERA he had a year ago as he ran away with the Cy Young Award voting.
But he has six no-decisions as well as a handful of other outings when he pitched well but the bullpen could not protect a lead or when the offense came up empty.
"It's just been one of those years ... 9-9, that's tough, it's not fun to be a .500 pitcher," Peavy said. "But I can't control wins and losses. That's baseball."
The victory on Sunday culminated a blissful homestand that saw the Padres go 5-1, all while facing the Diamondbacks' top three pitchers (Brandon Webb, Randy Johnson and Dan Haren) and Colorado's top three hurlers (Francis, Ubaldo Jimenez and Aaron Cook).