CLEVELAND -- Jason Giambi couldn't wait to get back to Cleveland. No joke.

With a chance to be Colorado's designated hitter for six straight interleague games, Giambi wanted to make the most of more playing time and more at-bats.

He's off to a great start.

Giambi's gigantic three-run homer in Colorado's six-run fifth inning off Fausto Carmona sent the Rockies to an 8-7 win Monday night over Cleveland, the Indians' first loss in seven games against the NL this season.

Giambi's 440-foot shot -- his 422nd career homer -- against Carmona (4-9) helped the Rockies win for the fifth time in six games and get back to .500 for the first time since May 25.

The 40-year-old Giambi will get extra swings on the road in AL ballparks for the next five games. This weekend, he'll be back in Yankee Stadium, where he starred in pinstripes from 2002-08.

After failing to get a hit in his first two at-bats, Giambi was eager to get to the plate in the fifth.

"I was crawling out of my skin," Giambi said. "By the third one I had calmed down a little. It was nice to contribute and help the ballclub win."

Leading 4-1 in the fifth, Carmona got two quick outs and had two strikes on No. 9 hitter Chris Ianetta before walking him. Following consecutive singles by Carlos Gonzalez and Chris Nelson, Carmona walked Todd Helton to force in a run. Troy Tulowitzki hit a hard hopper toward Orlando Cabrera -- playing his first game at third base in 15-plus seasons -- that caromed off the bag, bringing in two runs to tie it 4-all.

Giambi then crushed his seventh homer in just 52 at-bats, a blast that landed in the back of the Indians' bullpen in center field only a few feet from where reliever Chad Durbin was warming up. After Seth Smith doubled, Durbin replaced Carmona, who has been awful over the past month.

Giambi said he sat on Carmona's 3-1 pitch.

"I kind of bet the farm that he was going to throw me a fastball," said Giambi, wearing a black "Long Live Rock and Roll" T-Shirt. "I figured 3-1, be ready to hit and he just got one over the plate. He just left one up."

Rockies manager Jim Tracy has spent the past few days excitedly talking about the prospect of Giambi getting more playing time in interleague games.

"He's going to get a lot of at-bats and he's taken a big one already," Tracy said.

Matt Lindstrom (2-1), the second of five Rockies relievers, got the win. Huston Street worked the ninth for his NL-leading 21st save in 23 chances, getting the final out on a hard grounder that Helton snared at first.

Travis Hafner hit a three-run homer and Carlos Santana had a solo shot for the Indians, who collected 12 hits in their first game with new hitting coach Bruce Fields. He replaced Jon Nunnally, who was fired on Saturday.

Gonzalez had three hits for Colorado.

Considered the club's No. 1 starter, Carmona is 1-5 with a 9.73 ERA since May 19. He had no explanation for his fifth-inning collapse.

"I don't know what went wrong because it happened so fast," Carmona said through an interpreter. "I tried to get out of the inning, but it didn't work out. A couple of two-out walks really hurt. You can't do that with them. They have such a good lineup."

The Indians closed within 7-6 and chased starter Juan Nicasio in the bottom half on Shin-Soo Choo's two-run bloop single. Cleveland left the bases loaded, however, when Gonzalez ran down Cabrera's sinking liner in right-center to end the inning.

The Rockies tacked on a run in the eighth on catcher Lou Marson's throwing error.

Cord Phelps' two-out RBI single in the eighth got the Indians within 8-7, but the rookie was thrown out trying to go to second on the play. TV replays appeared to show he had beat the tag.

Santana's two-out homer in the fourth gave Cleveland a 4-1 lead. The switch-hitter, who has batted in five spots in manager Manny Acta's lineup, pulled a 1-0 pitch just inside the right-field foul pole for his 10th homer.

Hafner's shot into the seats in right put the Indians up 3-1 in the first. Hafner, in his fourth game back after missing 28 with a strained side muscle, hit a 2-2 pitch for his sixth homer -- and first since May 13, when he hit a walk-off to beat Seattle.

Carmona was in immediate trouble.

His first pitch was ripped for a single by Gonzalez, who stole second. Helton's bloop single moved Gonzalez to third and he scored on Tulowitzki's single. Carmona, though, managed to keep the damage minimal by getting Giambi on a flyout before first baseman Santana made a diving catch on Smith's liner headed for the corner.

Game notes
Giambi is tied for 73rd in career RBIs with Hall of Famer Joe Medwick (1,380). ... Since 2006, the Rockies are 51-31 in interleague play. ... The Rockies have brought their fathers on the trip to Cleveland and New York. On Tuesday, some of the dads will visit the Pro Football Hall of Fame in Canton. ... Choo has been showing signs of awakening from a season-long slump. He came in batting .438 (7 of 16) in his past five games. "Very encouraging," Acta said. "We know what's coming, a few of those balls are going to find their way to the seats." ... Rockies backup C Jose Morales had two pins surgically implanted in his right thumb. Tracy is encouraged Morales could be back by the end of the season, but will definitely be out "a couple months."