DENVER — Taijuan Walker's second straight great outing was wasted with a late-game collapse by the Seattle Mariners bullpen.
Walker followed his one-hit gem against Minnesota by pitching effectively into the eighth Wednesday, but the Colorado Rockies rallied to win 7-5 in 11 innings on Michael McKenry's two-run homer.
McKenry hit Mayckol Gauipe's 2-2 curveball into the left-field seats for his fourth home run of the season and the first walk-off hit in his career.
"I left a slider up and he hit it good," Guaipe said.
Seattle's Nelson Cruz doubled and singled to extend his hitting streak to 16 games but failed to homer for the first time in six games.
Walker built on Saturday's win over the Twins with 7 1-3 innings of mostly dominant ball despite not feeling sharp. He allowed five hits and gave up Carlos Gonzalez's three-run homer in the sixth.
"My stuff wasn't really working," Walker said. "The curveball wasn't working like I wanted. My changeup and curve weren't there."
Still, he was in line for the win after Franklin Gutierrez hit a tiebreaking two-run homer in the seventh to give Seattle a 5-3 lead. The Rockies rallied to tie it in the ninth off closer Fernando Rodney.
"The walk hurt (Rodney)," Mariners manager Lloyd McLendon said. "These type of ballparks and you walk guys or you misplay a ball, it usually comes back to haunt you."
The Rockies' winning rally started with Ben Paulsen's one-out single off Guaipe (0-3). McKenry worked the count even before he delivered his big hit.
"You make mistakes in this ballpark it's likely to go out," McLendon said. "And it did."
Yohan Flande (2-1) pitched the top of the 11th to get the win.
Seattle scored three runs in the fourth, with Walker hitting an RBI double. It was his first major league hit.
Colorado, which managed just two hits through the first five innings, rallied to tie it in the sixth on Gonzalez's 22nd home run, which traveled an estimated 465 feet.
"I looked at (bench coach Tom Runnells) after CarGo's homer and said, 'These guys are killing us 3-3.' That's what it felt like," Rockies manager Walt Weiss said. "Walker was in complete control of the game and he was pretty filthy. To get three runs with one swing, that was pretty huge."
Gutierrez finished with three hits for the first time since doing it at Detroit on Sept. 18, 2013.
The Mariners suffered their eighth walk-off loss of the season. Since the beginning of the 2010 season they have suffered 63 walk-off losses, which is most in the major leagues.
Mariners: RHP Hisashi Iwakuma (2-2, 4.47) will open a three-game series at home against Texas on Friday. Iwakuma tossed 8 2-3 innings of one-run ball against Minnesota on Sunday.