They scored four runs in the first inning against the Colorado Rockies right-hander and knocked him out after three on the way to a 10-0 win Tuesday night.
The Giants, who have won four straight games and 21 of their past 26, are hitting .424 (59 for 139) against Cook (4-8), who is 8-11 lifetime against the Giants.
"I don't have anything to give you that says, 'Why,'" Giants manager Bruce Bochy said. "Come in here and you're hoping to put some runs on the board, and that's what we did early."
Jonathan Sanchez (8-6) limited the Rockies to three hits over six innings. After five straight no-decisions, he won for the first time since July 5 and equalled his 2009 victory total. Bochy said had Sanchez not felt ill, he wouldn't have removed him after a leadoff walk in the seventh.
Nonetheless, Sanchez, who threw a no-hitter July 10, 2009, finished with nine strikouts. He struck out seven straight at one point, tying the Giants record set by Hall of Famer Juan Marichal on Sept. 6, 1964, at Philadelphia.
Sanchez said he wasn't aware how many consecutive strikeouts he had and learned he had tied Marchial when he came into the clubhouse at the end of the fourth inning and heard it announced on television.
"When he did it, he was nasty the whole time -- Juan Marichal," Sanchez said. "That's the way I feel tonight. After the first inning, they were swinging on pitches not over the plate -- in the dirt. I was getting ahead the whole time, so they had to swing.
The Giants chipped away at Cook for four runs in a 36-pitch first inning. After Cook issued a one-out walk, putting runners at first and second with one out, consecutive singles by Buster Posey, Pat Burrell, Travis Ishikawa and Pablo Sandoval resulted in four runs. Sanchez added a fifth single, but left fielder Ryan Spilborghs threw out Ishikawa at the plate to end the inning.
Cook retired the side in order on seven pitches in the second but gave up a one-out homer to Burrell in the third. Burrell is 15 for 24 (.625) against Cook with one double, two homers and seven RBIs, which is the highest average by any player, active or retired, with a minimum of 20 plate appearances against Cook.
"I have trouble with Pat Burrell," Cook said. "There are a lot of guys that have had success against me. I have been pitching bad the last couple of starts and they took advantage of it tonight."
Cook is 0-3 with a 13.97 ERA in his past three starts. His spot in the Rockies' rotation seems uncertain, but manager Jim Tracy wouldn't address that after the Rockies were shut for the fourth time this season, the second at home and suffered their most lopsided home loss of the season.
"I'm not a guy that walks in after a game like that and starts talking out loud about things," Tracy said. "There will be a better time than tonight to talk about that."
The Rockies were held to three hits, matching their season-low. In addition to singles by Todd Helton, who was activated Tuesday and played his first game for the Rockies since July 4, and pitcher Taylor Buchholz, Melvin Mora doubled in the sixth.
The Giants matched their season-high with 19 hits, the most allowed by the Rockies this season, and assured themselves of a split of the two-game series. The last time the Giants were at Coors Field they lost three of four, dropping the final game of that series 4-3 in 15 innings. Since that 5-hour, 24-minute marathon, the Giants have gone 21-5.
"The most important thing is we start this road trip with a win," said Bochy, referring to the Giants' six-game trip to Colorado and Atlanta.
Buchholz relieved Cook and gave up a run-scoring single to Posey in the fifth and a solo homer to Freddy Sanchez in the sixth. Posey, who is hitting .356 since being recalled May 29, went 3 for 5. He and Burrell each had two RBIs.
"There's not a whole lot to say about tonight," Tracy said. "The game didn't start right for us. The way they started offensively with a four-run first inning that put us in a hole. By the third inning they were ahead 5-0 after Burrell's home run. And offensively, I would have liked to have dealt with Sanchez in a game that was a lot closer where we could have had chances to change the complexion of the game. It wasn't going to happen tonight."
Rockies CF Dexter Fowler was unavailable Tuesday after bruising his left hip and ribs when he hit the wall making a catch Sunday. Tracy said Fowler won't start Wednesday but might be able to play. ... Giants RHP Todd Wellemeyer (right quad strain) will make his last rehab start Wednesday for Triple-A Fresno at Round Rock. ... The Giants have won five straight games on the road and are 29-25 (.537) away from home this season.