DENVER (AP) -- Colorado Rockies left-hander Jorge De La Rosa was bothered by a cut on the middle finger of his pitching hand in his previous start.
The cut checked out fine before his outing Wednesday night, but De La Rosa was no match for Washington's Ross Ohlendorf.
The Nationals brought him up from Triple-A, and he shut down the Rockies for six innings in Washington's 5-1 win.
De La Rosa (7-4) had won five straight games over a seven-start stretch and lost for the first time since April 30. He allowed four hits, three walks and three runs in 5 1-3 innings.
"He struggled through some of this outing and again in the end kept us close enough to win a game," Rockies manager Walt Weiss said. "He had to work pretty hard, threw a lot of pitches. Kept us in striking distance."
De La Rosa allowed a run in the fourth on a two-out single by Ian Desmond, who extended his career-high hitting streak to 14 games.
After a one-out walk to Jeff Kobernus in the sixth, Ryan Zimmerman doubled to the wall in deep left-center, scoring Kobernus.
Left fielder Carlos Gonzalez and center fielder Dexter Fowler both converged on Zimmerman's drive, banging into each other as Fowler jumped at the wall. The ball dribbled onto the ground and Fowler threw it back in. Both players, though shaken up, remained in the game.
Adam Ottavino relieved De La Rosa and Wilin Rosario replaced catcher Yorvit Torrealba in a double switch.
One out later, Adam LaRoche was walked intentionally and took second on a wild pitch before Desmond singled up the middle, scoring Zimmerman and LaRoche.
Ohlendorf pitched six strong innings and allowed two of the Rockies three hits in his Washington debut.
The Nationals signed him to a minor league contract in January. A rainout Friday forced the Nationals to play a doubleheader Sunday and resulted in the need for a starter Wednesday. They brought up Ohlendorf, 30, from Triple-A Syracuse.
"He mixed it up basically, never really fell into patterns," Weiss said. "Used his fastball well. Used his breaking ball well off of that. There's some deception. We never really figured him out."
Ohlendorf gave up a bunt single to Jonathan Herrera in the first and he reached second on a throwing error.
Ohlendorf then retired 12 straight batters before he walked Nolan Arenado with one out in the fifth. The Rockies broke through against Ohlendorf in the sixth when Herrera grounded into a fielder's choice, and Gonzalez hit a two-out triple.
"It's not easy in this ballpark, just an outstanding job," Nationals manager Davey Johnson said. "I'm going to try to find a way to keep him around."
Ohlendorf has gone to an over-the-head windup this year, which he said helps his rhythm and helps him stay loose. The delivery perplexed the Rockies.
"Sometimes you get ready too early," Arenado said. "Then you get ready too late. You couldn't find that balance. He kept the ball down. He mixed in both sides of the plate. You've got to give him credit. He did a good job."
NOTES: Nationals C Wilson Ramos re-injured his left hamstring running first-to-third drills two days ago at the club's facility in Viera, Fla. Manager Davey Johnson termed it a slight setback but said it would be "a long shot" for Ramos to return before the All-Star break. ... The Nationals made room for Ohlendorf by optioning RHP Nathan Karns to Double-A Harrisburg. ... The Rockies announced prior to the game that they had signed their top draft pick, Oklahoma pitcher Jonathan Gray. The third overall selection in last week's draft, Gray is the highest draft pick so far to sign with his team. ... OF Eric Young Jr. was designated for assignment by the Rockies, and RHP Chris Volstad recalled from Triple-A Colorado Springs... OF Michael Cuddyer missed a fifth straight game for the Rockies because of a right ribcage strain, but is expected to return for Thursday's series finale against Washington.
Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.