"He was real aggressive tonight," manager Matt Williams said of Harper. "He got the head out on the fastball. Hopefully, it's a sign of good things to come."
Washington's other run came an inning later, after Burnett exited, when Ryan Zimmerman doubled down the left-field line to drive in Jayson Werth.
"Burnett has been tough on us. He beat us twice here, but we got him at home," Williams said. "The ball moves. He is pretty good. He has an idea of what he wants to do and how he wants to attack hitters. He had [all his pitches] working tonight -- curveball, certainly his sinker to both sides of the plate and the changeup, too."
But the loss to Philadelphia was not the biggest blow of the night. That came in the fourth inning, when Nationals right-hander Jordan Zimmermann left the game with a biceps cramp. He was scheduled to have an MRI exam on Saturday.
Williams did not seem to think the injury was serious, but he did say that Zimmermann would not pitch in Tuesday's All-Star Game. It marked the second year in a row that Zimmermann was named to the All-Star team before being sidelined from the game with injury. Last year, Zimmermann had neck problems. It was not immediately clear who would replace Zimmermann on the National League roster.
"The doctor checked him out; there doesn't seem to be an issue with the shoulder or the elbow," Williams said. "It seems to be in the belly of the muscle. We are going to get an MRI in the morning. I think Jordan feels OK about it."
The count was 2-2 to Phillies catcher Cameron Rupp when Zimmermann summoned Williams to the mound. Pitching coach Steve McCatty and athletic trainer Lee Kuntz also went to the hill. About a minute later, Zimmermann was taken out of the game in favor of reliever Craig Stammen, who struck out Rupp on one pitch.
Stammen is used to entering a game after a pitcher gets injured. On Aug. 21, 2010, Stammen replaced Stephen Strasburg after Strasburg hurt his elbow against the Phillies.
"It does cross my mind, because I know [Zimmermann] is not going to come out of the game unless he is probably hurting too bad," Stammen said.
Zimmermann said he started to feel tightness in his arm in the third inning and that the injury was worsening with each pitch. After the game, though, Zimmermann said he felt OK.
"It was getting a little tight in the last inning, and every pitch it was getting tighter and tighter," Zimmermann said. "It was cramping up. I didn't want to push it too far and have something worse happen. I figured it would be best if I came out. We are going to get an MRI and see. It's pretty much muscle in the middle of the biceps. I think it should be fine."
It was not a good night for Zimmermann before the injury. Over 3 1/3 innings, he allowed four runs on six hits. The Phillies scored their first two runs in the second inning when Domonic Brown doubled in Marlon Byrd and Cody Asche. An inning later, Rollins hit a two-run homer to make it a 4-0 game.
"The command wasn't really there. I made a few mistakes," Zimmermann said. "They were jumping on the first-pitch fastball. … They were squaring me up pretty good."
Stammen lasted 3 1/3 innings and allowed two runs on four hits. Philadelphia scored its fifth run in the sixth inning on a double by Rupp. An inning later, Rollins hit a second home run, a solo shot over the right-field wall. It was Rollins' ninth career multihomer game.
"That simple. Really, that simple," Rollins said. [I'm not] any stronger. Just being able to get to that stroke. Being able to catch the ball in the right spot and get some good flight on it. Picking pitches. Getting situations where they're giving me the pitch and capitalizing."