DENVER -- Johnny Cueto wasn't going to let a little back tightness bother him.

Resorting to his herky-jerky motion less than usual, Cueto won his fifth consecutive decision Sunday and continued his mastery of both the Colorado Rockies and Coors Field in the San Francisco Giants' 8-3 victory.

The win was the 15th in 17 games for the Giants, a stretch in which their starting pitchers have gone 10-1 with a 1.53 ERA.

Cueto (8-1) added to that gaudy streak by allowing two runs (one earned) and six hits in six innings to lower his ERA to 2.31. He is the first Giants pitcher since Shawn Estes in 1997 to win at least eight of his first 11 starts.

In his past seven starts, Cueto is 5-0 with a 1.69 ERA. He is 5-2 with a 2.35 ERA in 10 career starts against the Rockies and 4-1 with a 2.43 ERA in six outings at Coors Field.

"Seems like I concentrate more when I'm here, knowing they have great hitters," Cueto said through a translator.

Cueto said he felt tightness in his upper left back after the first inning but wasn't in discomfort on the mound.

Summing up his outing, he said, "Today I had nothing on the ball, but everything came out well."

He came up to the clubhouse a couple of times between innings to have his back stretched but emphasized that his back was not the cause of his diminished stuff.

The Giants pounded out 17 hits, including eight doubles to tie the record for the San Francisco era of the franchise dating from 1958.

Before Saturday's game, Giants catcher Buster Posey called a hitters meeting. At that point, San Francisco had scored three or fewer runs in six of its past nine games. The Giants erupted for six runs in the eighth Saturday and finished with 16 hits in a 10-5 win, then carried that offensive onslaught into the rubber game of the series.

Hunter Pence had a career-high three doubles and three RBIs on Sunday. Brandon Belt had two doubles and two RBIs. Brandon Crawford had a run-scoring double. Posey and Gregor Blanco each had three hits, including a double, while Denard Span had three hits, including a home run.

Rockies starter Chris Rusin (1-3) worked five innings and failed to set the Giants down in order in any of them. He gave up six runs on 11 hits and three walks.

"He got some pitches elevated," Rockies manager Walt Weiss said. "I don't know if the wheels came off. He was pitching through a lot of traffic. But the fact that he got through five, it was pretty big for us because we weren't set up in the bullpen to take on many innings today.

"It could've been worse. We kept the bullpen intact. He didn't have his 'A' game, but he minimized a lot of damage."

Span, who missed Saturday's game with a bruised right hip, led off the fourth with his second homer, a 441-foot drive into the second deck in right field that put the Giants ahead 6-2. It was the first homer off Rusin in 39 2/3 innings this year and the 14th in Span's career.

"I'm always hitting balls in the gap, hitting balls on the ground and having to sprint," Span said. "So it feels good to jog around the bases. It feels good when you hit a ball like that."

Cueto forced in a run by walking Nolan Arenado, who has hit 17 career homers against the Giants, with one out and the bases loaded in the third. However, Cueto kept the score at 5-2 when Gerardo Parra hit a soft low liner to first baseman Belt, who doubled Arenado off first.

It didn't take long for the Giants to get to Rusin. Pence, who doubled home a run in the second, did it again in the third, and Belt followed with a two-run double to put the Giants ahead 5-1.

Cueto had allowed just two homers in 75 2/3 innings in his previous 10 starts before Trevor Story belted his 14th homer in the second, cutting the Giants' lead to 2-1 and ending Cueto's scoreless streak at 17 innings overall and 19 1/3 against the Rockies.

The home run came after center fielder Span threw out Parra, who tagged up and tried for third on a fly ball after opening the inning with a double.

"That's a huge play," Giants manager Bruce Bochy said. "(Otherwise) they got a man on third with one out there."

NOTES: Rockies CF Charlie Blackmon went 1-for-5, extended his career-high streak of consecutive games reaching base to 24. ... Rockies C Nick Hundley (strained left oblique) is scheduled to play games in extended spring training Monday and Tuesday and begin a rehab assignment Wednesday with Triple-A Albuquerque. ... Rockies RHP Adam Ottavino is scheduled to throw his second batting practice Tuesday since undergoing Tommy John surgery May 7, 2015. Barring a setback, Ottavino will join high Class A Modesto on June 9 to begin a rehab assignment. ... Giants 2B Joe Panik was given a planned day off. ... Giants RHP Sergio Romo (flexor strain) is scheduled to make back-to-back appearances Sunday and Monday for Triple-A Sacramento before joining the Giants.