WASHINGTON -- Coming off one of his worst outings of the season, Washington starter Jordan Zimmermann surrendered a pair of first-inning hits against Colorado on Thursday night.
That only gave the Rockies false hopes.
Zimmermann pitched eight innings to win his 10th game, Adam LaRoche had three hits including a two-run triple and the Nationals spoiled Roy Oswalt's return to the majors with a 5-1 win over Colorado on Thursday night.
Ian Desmond homered for the second straight game and Denard Span and Steve Lombardozzi added a double and a single apiece for Washington, which began a stretch in which it will play 14 of its next 17 games at home.
"What a game he pitched. We needed it," Nationals manager Davey Johnson said of Zimmermann. "(After an) 11-inning game last night, that was a Godsend."
Zimmermann (10-3) allowed an unearned run on six hits, returning to form after surrendering six runs and eight hits in five innings Saturday in Cleveland.
"I felt like I threw the ball well and had good fastball command, my slider was good and I got a big strikeout in the last inning there on a changeup," Zimmermann said.
"I was throwing strikes and getting ahead of guys. I know they're an aggressive team and that kind of works in my favor. Throw some first pitch strikes and let them hit the ball."
Zimmermann retired 16 straight in one stretch, throwing 112 pitches -- 85 for strikes -- while fanning nine and walking one.
Colorado finally got to Zimmermann in the eighth. Pinch hitter Josh Rutledge singled, Anthony Rendon committed a throwing error after fielding Tyler Colvin's grounder and Rutledge ended up on third. DJ LeMahieu singled to score Rutledge, but Zimmermann struck out Carlos Gonzalez on a changeup and Michael Cuddyer to end the threat.
"He's starting throwing it more often, he started to get more confidence and now it's a pretty good pitch," catcher Kurt Suzuki said of Zimmermann's changeup.
Oswalt (0-1) went five innings in his Colorado debut, allowing four runs on nine hits. He struck out 11 and didn't walk a batter.
"I felt strong," Oswalt said. "Overall felt pretty well, just, it's hard to say this, but really too many strikeouts. Kind of got my pitch count up and I was trying to get deeper into the game."
The 35-year-old right-hander was signed to a minor league contract May 2, and went 3-2 with a 2.16 ERA in five starts for Double-A Tulsa before being called up.
"I thought Roy threw the ball extremely well, punched out 11 in five innings," Colorado manager Walt Weiss said. "Plenty of stuff, plenty of arm, a really good fastball. I thought he had a few tough breaks, the line could have been better than what it showed."
Todd Helton and LeMahieu had two hits for the Rockies, who have lost the first four games of a nine-game road trip and fell to .500 for the first time since April 2.
Desmond, who hit a grand slam in the 11th inning of Wednesday's 6-2 win at Philadelphia, homered his first time up Thursday night to put Washington ahead 1-0 after two.
LaRoche led off the Washington fourth with a single. After Oswalt fanned Jayson Werth and Desmond, Lombardozzi singled. Kurt Suzuki then hit a grounder between third and short that shortstop Jonathan Herrera managed to deflect. Herrera retrieved the ball in short left, but LaRoche raced around from second and was safe on a close play at home to make it 2-0.
"That feels good, when you've been lining out at people to get a hit like that feels nice," Suzuki said.
LaRoche provided some insurance in the fifth when he tripled with one out, scoring Span and Rendon.
Zimmermann drove in the Nationals' fifth run with a sacrifice fly -- the first of his career -- in the sixth.
Washington, which began play second in the NL East, won its second straight and picked up a game on division leader Atlanta.
"Obviously it's nice to pick up a game," LaRoche said. "We need to get ourselves on track and play some consistent ball. I don't need to tell you we've been way too streaky."
Johnson said before the game that OF Bryce Harper (left knee bursitis) ran in the outfield Thursday and was going to take swings in the indoor batting cage as he nears a rehabilitation assignment. "He's close," Johnson said. "If it doesn't swell up tomorrow, as far as I'm concerned, he can play some.". Cuddyer extended his hitting streak to 18 games. ... Washington OF Roger Bernadina, who missed Wednesday's game with eye irritation, entered the game in the ninth. ... To make room for Oswalt, the Rockies optioned LHP Jeff Francis to Triple-A Colorado Springs and designated RHP Chris Volstad, who was at Colorado Springs, for assignment. Rockie CF Dexter Fowler (right ring finger) missed his third straight game. ... Colorado RHP Tyler Chatwood (4-1, 2.33) opposes Stephen Strasburg (3-6, 2.50) Friday.