DENVER -- The Colorado Rockies are glad Michael Tucker is leaving town.

Tucker hit his second grand slam against Colorado this season and drove in five runs, rallying the San Francisco Giants to an 8-6 victory Sunday.

"He's a hot hitter, and when he came up in the seventh we had limited options," Rockies manager Clint Hurdle said. "My starter had thrown 112 pitches and my bullpen was down to a couple of pitchers."

Tucker, who had two homers and seven RBI the past two days, added an RBI double. Edgardo Alfonzo had three hits and scored three times for the Giants, who took two of three at Coors Field before heading to San Diego.

Tucker also hit a grand slam against the Rockies on April 9.

"It was the same situation as last time," Tucker said. "People got walked ahead of me and I made them pay for it."

Four San Francisco relievers combined to allow just one run and three hits in six innings. Matt Herges (1-0) recorded five outs to earn the win.

Armando Benitez worked the ninth for his third save. He allowed Todd Helton's first home run of the season.

"Our bullpen really picked us up," Giants manager Felipe Alou said. "They gave us six strong innings when we needed it."

Trailing 5-3 in the seventh, San Francisco loaded the bases on three walks, the first two issued by starter Jason Jennings.

"I knew I was done when I walked Pedro Feliz," said Jennings, who remained winless despite striking out eight. "I wasn't going to face Alfonzo, the hottest hitter in the league right now."

Byung-Hyun Kim (0-2) relieved with two outs and walked Alfonzo on four pitches. Tucker hit the next pitch into the Colorado bullpen in right field for his second career slam and a 7-5 lead.

"Bad pitch," Kim said. "Bad location."

As soon as he hit the ball, Tucker was sure it was gone.

"I knew I had hit it good," Tucker said. "I was thinking we had taken the lead and we could just go from there."

Alfonzo added an RBI groundout in the ninth.

The Giants fell behind 5-1 as starter Kirk Rueter lasted only three innings, allowing five runs and 10 hits. Jennings drove in a run with a groundout, and Clint Barmes had an RBI single.

In the third inning, Jeff Baker had an RBI double and Michael Restovich drove in a run with a single.

San Francisco scored twice in the fourth to make it 5-3. Alfonzo and Tucker hit consecutive doubles, and Ray Durham had an RBI single.

Alfonzo also doubled in the second and scored on Marquis Grissom's single.

Notes

Yorvit Torrealba caught for the Giants to give Mike Matheny a day off. ... Grissom turned 38. ... The Giants made two errors, giving them 10 in the first 11 games. ... Jennings hasn't won in 11 starts since Aug. 17. ... Rockies RHP Aaron Cook had a bullpen session and continues to show progress after two operations to relieve blood clots in his lungs.