DENVER (AP) -- Winding down a brutal season, the Colorado Rockies ran smack dab into another low point.
Colorado couldn't hold an early six-run advantage, blowing its biggest lead in a loss this season, and fell 12-7 to the San Francisco Giants on Tuesday night.
"It was a bad loss," Rockies manager Walt Weiss said. "Two different games really. It wasn't pretty."
Buster Posey accounted for much of the damage, leading the Giants back by homering, doubling twice and driving in four runs.
Posey's solo shot in the sixth keyed a three-run burst as the Giants raced back from a 7-1 deficit to remain on the heels of the Los Angeles Dodgers in the NL West. He added a two-run double in a six-run seventh.
Hunter Pence had two hits to extend his hitting streak to 15 games for the Giants.
George Kontos (4-0) kept the Giants in striking distance with 1 2-3 scoreless innings until the bats could heat up.
When they did, the Rockies couldn't cool them off, as starter Jordan Lyles allowed six runs in 6 1-3 innings before giving way to reliever Matt Belisle (4-7), who surrendered another four before being pulled after getting just one out.
"We were pretty efficient early on," Lyles said. "The sixth, I gave up a homer to Posey. I fell behind and I'm not going to walk him there with a six-run lead. I left it right down the middle and he put it in the seats."
Two outs later, Lyles had Andrew Susac down 0-2 before the Giants' catcher connected for a two-run shot, pulling San Francisco to 7-4.
"I just didn't make a good pitch to Susac," Lyles said. "I had a chance to put him away, got ahead of him and I just left one over the plate. He hit it a long way."
A seventh inning that featured five extra-base hits began with pinch-hitter Matt Duffy grounding out. But Lyles then walked Angel Pagan and Joe Panik doubled. Belisle relieved Lyles and promptly was hammered for a two-run double by Posey, an RBI single from Pence, a run-scoring double by Gregor Blanco that gave the Giants the lead, an RBI double from Susac. Nick Masset relieved Belisle and gave up a run-scoring triple to Brandon Crawford.
Josh Rutledge had a two-run triple in the third and DJ LeMahieu followed a two-run homer for the Rockies, who have the worst record in the National League.
Lyles kept the Giants bats at bay with a new grip on his changeup until unraveling in the sixth.
Yusmeiro Petit was hit hard, allowing six runs in four innings but was let off the hook with a no-decision by his team's comeback. The righty shut down the Rockies when he faced them last week.
Giants: OF Michael Morse suffered a strained oblique in batting practice Monday. Manager Bruce Bochy said he expects Morse to return soon.
Rockies: OF Michael Cuddyer (strained left hamstring) said he's healthy and will be ready to come off the disabled list when he's eligible next week. In his down time, Cuddyer said he's drafted four different fantasy football teams.
Giants: RHP Ryan Vogelsong (8-9, 3.73) has given up eight earned runs in 6 1-3 innings against Colorado this season.
Rockies: RHP Christian Bergman (1-2, 5.74) didn't give up a hit until the fifth in his last start at Arizona. He went 5 1-3 innings in a no-decision.
CRAZY COORS FIELD
Giants manager Bruce Bochy felt for Weiss having to play half his games in such a hitter friendly park.
"I don't know how Walt does it," Bochy said. "It's a different game."