Kris Medlen struck out a career high 12 to lead the Atlanta Braves to a 6-1 win over the Colorado Rockies on Monday.

Medlen (7-1) allowed five hits without a walk in his second complete game of the season.

He extended his streak of scoreless innings to 34 2-3 — the Braves' longest since Greg Maddux in 2000 — before the Rockies scored an unearned run in the seventh.

The right-hander, who appeared in 38 games in relief before moving into the rotation on July 31, improved to 6-0 with a 0.54 ERA in seven starts. He spent most of 2011 on the disabled list recovering from elbow ligament-replacement surgery on Aug. 18. 2010.

Medlen was 5-0 as a starter in 2010. The Braves have won his last 18 starts. He threw 111 pitches, including 85 strikes.

David Ross hit a two-run double in Atlanta's four-run third inning.

Rockies starter Tyler Chatwood (4-4) gave up six runs, five earned, in only three innings. Chatwood allowed only two hits but was hurt by five walks, matching his career high.

Chatwood loaded the bases with three walks in the third. Martin Prado drove in Michael Bourn with a flyball to centerfield. Juan Francisco's single drove in Jose Constanza. Ross added a two-run double for a 6-0 lead.

Two walks and a wild pitch by Chatwood and two errors on one play by first baseman Jordan Pacheco helped the Braves score two runs in the first. After walks to Bourn and Freddie Freeman, Bourn scored from third on a wild pitch. Prado hit a sharp grounder off Chatwood's left leg. Pacheco couldn't handle Chatwood's throw to first base, and Pacheco then made a wild throw to third base for another error, allowing Freeman to score.

Medlen had not allowed a run since Aug. 11, when he gave up only one run in a 9-3 win at the Mets. A throwing error by shortstop Paul Janish helped the Rockies score an unearned run in the seventh inning.

Carlos Gonzalez singled and scored from first when Janish dove for Pacheco's grounder and threw wild to second base for an error. Pacheco advanced to third on his single and Janish's error, but Medlen struck out Tyler Colvin and Chris Nelson to end the inning.

Medlen's streak of scoreless innings was the longest for a Braves pitcher since Maddux did not allow a run in 39 1-3 consecutive innings from Sept. 2-28, 2000.

Prado made his second straight start at second base as Dan Uggla said before the game he was told by manager Fredi Gonzalez Sunday he has lost his starting job.

Uggla, who started in this year's All-Star game, is hitting only .208.

"He didn't really explain anything to me," Uggla said. "He just kind of said, 'We've got to make a change. I don't know how much playing time you're going to get the next 29 days.'"

Prado played in left field most of the season but has experience at second base and third base.

"It's a situation where we feel like we need to do something for the team and the name on the front of the uniform," Gonzalez said. "It's hard. It's not easy. Two months ago, you don't even think about it."

NOTES: Pacheco has a 12-game hitting streak. ... Medlen's previous career high was nine strikeouts. ... RHP Randall Delgado, recalled from Triple-A Gwinnett, will pitch out of the Braves' bullpen. Delgado was 4-9 with a 4.42 ERA in 17 starts with Atlanta before he was sent to Triple-A Gwinnett on July 15. ... C Brian McCann, who had a cortisone shot in his right shoulder after Saturday's game, missed his second straight start. ... Rockies SS Troy Tulowitzki, on the 15-day DL with a groin injury, played as a DH on Monday with Triple-A Colorado Springs and is scheduled to play shortstop with Double-A Tulsa Wednesday and Thursday. ... Braves RHP Tommy Hanson will try for his 13th win against Colorado LHP Drew Pomeranz (1-8) on Tuesday night.