WASHINGTON -- Stephen Strasburg entered Saturday's game with an ERA of 5.16 this season and a pedestrian record of 5-5.

But Colorado was exposed to vintage Strasburg, who struck out a season-high 12 batters and walked none in seven innings while giving up just three hits as the Washington Nationals beat the Rockies, 6-1.

"His stuff was electric," right fielder Carlos Gonzalez said of Strasburg, who lowered his ERA to 4.76. "His curve is really sharp. It goes down quickly to the ground. He's a really good pitcher. It was a great game overall for them and Stras did his part. I knew it was going to be a battle from the start."

Colorado manager Walt Weiss also was impressed with Strasburg (6-5), who also had a career-high three hits in as many at-bats as he came off the disabled list to make his first start in more than a month.

"That was top-shelf stuff," said Weiss, whose team matched its season-low hit total. "It was going to be tough to score off him. Stras did not give us much in the middle of the plate."

Saturday was the 17th time he reached double digits in strikeouts. His career best is 14, which he recorded in his major league debut in 2010.

"He's one of the best in baseball when he's out there doing his thing, painting 98 on the black, reaching 99 sometimes," Washington right fielder Bryce Harper said of Strasburg. "Great curveball, good change-up. He's very good out there. To come back for his first game and do what he did tonight ... establish his fastball early and never [looked] back."

The right-hander struck out at least one batter each inning and fanned every starter in the Colorado lineup at least once except left fielder Brandon Barnes. First baseman Ben Paulsen and second baseman DJ LeMahieu whiffed in their three trips to the plate against Strasburg, who threw only 91 pitches.

"I'm just trying to go out there and do everything I can to help them win some ballgames. At this point, I just want to take it one game at a time," Strasburg said. "I just want to go out there and compete and leave it all out there on the field. It's definitely been an up and down year, and it's been a huge learning experience, so I'm excited to have another opportunity."

Washington (57-52) won for just the third time in nine games and Colorado (46-62) fell to 21-33 on the road. The Nationals pulled to within 1 1/2 games in the National League East of the first-place New York Mets, who lost 5-4 at Tampa Bay.

"Fastball command was there, curveball command was there," Washington manager Matt Williams said of Strasburg. "He threw some really good change-ups as well to the lefties, and he hit. If he's got a fastball down and away to right-handers early on, then he's got a lot of weapons. He felt good coming in.

"I thought he was in command all night. He kept them in check. I know he's pleased with it. We're all pleased with it."

The Nationals made it 6-1 in the seventh with an RBI single by first baseman Ryan Zimmerman, his second run-scoring hit of the game. Harper, who also had two hits, then scored when left fielder Clint Robinson hit into the fourth double play of the night by Washington.

Blake Treinen came on to pitch a scoreless eighth for the Nationals and Matt Thornton took over in the ninth to get the last three outs.

The losing pitcher was Colorado starter Eddie Butler (3-9), a Virginia native who has not won for the Rockies since May 30. He gave up four runs, eight hits and four walks in six innings.

"Some good things from Eddie. There was a lot of damage control. He kept us in the game; he got through six. I thought he battled and I thought he threw the ball really well," Weiss said of Butler.

"It was cool. They are out there rooting you on," Butler said of pitching in front of family and friends. "They support me all of the time. To have them here in the stands was nice."

NOTES: Washington RF Bryce Harper entered Saturday having reached base in eight of his last 10 at-bats. He was leading the majors in on-base average at .463, and is far above some of his everyday teammates, including LF Jayson Werth (.258), SS Ian Desmond (.267) and C Wilson Ramos (.265). ... The series ends Sunday with Washington RHP Max Scherzer (11-8, 2.31) facing Colorado LHP Yohan Flande (2-1, 3.54). ... Rockies 1B Carlos Gonzalez, who hit a grand slam on Friday, entered Saturday with 23 home runs and 60 RBIs. Last year he hit 11 home runs and his career high was 34 in 2010. Since the All-Star break, he leads the National League with 10 home runs and 25 RBIs. ... The Nationals went 20-5 from late April to May 25 to improve to 27-18. Since then they were only 29-34 in games through Friday.