WASHINGTON -- Bryce Harper flipped his bat behind him, clenched his fists and looked into the Washington Nationals' dugout as he began his trip around the bases.

After striking out in his first three at-bats, Harper hit a hanging curve for a tiebreaking three-run homer in the eighth inning off lefty Patrick Shuster as the Nationals posted a 3-0 victory over the Philadelphia Phillies on Saturday.

"I was just trying to get a pitch I could drive," said Harper, who is hitting .250 with 24 homers and 80 RBIs. "I got pretty good wood on it. Down the stretch you want to win as many games as you can. We have to lock this (division title) up. We have to play the best of our abilities."

Harper joked that he probably would have swung had the 3-1 pitch been in the opposing dugout.

"I got a pitch over the middle of the plate," said a surprised Harper.

Seconds after Harper said those words, teammate Chris Heisey let out a shout at the other end of the Nationals' clubhouse after he watched the Atlanta Braves defeat the New York Mets. That gave the first-place Nationals (84-58) a nine-game lead over the second-place Mets in the National League East.

"That's just a great team win," said Washington starter Max Scherzer, who pitched 6 2/3 innings of shutout ball but did not figure in the decision.

Former Phillie Ben Revere singled with one out in the eighth off Luis Garcia (1-1) and took second on a wild pitch by Shuster, who had come on to face Daniel Murphy. After a walk to Murphy put runners on first and second, Harper hit a 78 mile-per-hour pitch from Shuster into the Washington bullpen down the right-field line for his first homer since Aug. 28.

Phillies manager Pete Mackanin was more annoyed by the walk to Murphy than the homer by Harper.

"It wasn't a great audition. You have to throw strikes," Mackanin said of lefty Shuster. "(Harper) is a quality hitter. If you make mistakes he is going to hurt you."

The Phillies (63-79) have lost 11 of their last 12 games to Washington.

The Nationals' Shawn Kelley (2-2) retired Tommy Joseph with a runner on second for the final out of the eighth. Washington closer Mark Melancon pitched the ninth for his 40th save of the season, and 10th with the Nationals.

"That is why we traded for him," Washington manager Dusty Baker said of Melancon, acquired from the Pittsburgh Pirates in late July.

Scherzer, who lowered his ERA to 2.78, threw 117 pitches against the Phillies. He allowed four hits and no runs with eight strikeouts.

"I didn't think he was at his best tonight," Mackanin said. "He's an elite pitcher. I've seen him much better."

The veteran right-hander was taken out with a runner on first and two outs in the seventh by lefty Marc Rzepczynski. The veteran reliever retired pinch-hitter Maikel Franco -- making his first appearance since Tuesday - on a fly to right to end the inning.

The Phillies starter was Jerad Eickhoff, who had won four of his previous five decisions. He went six innings and allowed no runs on five hits with five strikeouts before he was lifted for a pinch-hitter in the seventh.

"That was a great pitching performance by him," Mackanin said. "He mixed his pitches pretty well. He fought, he works hard. He was really good. I kind of expected him to be this kind of pitcher. He doesn't get rattled. He looks like he's out there to beat you."

Cesar Hernandez had two hits for the Phillies and backup catcher Jose Lobaton and Revere had two for Washington.

Scherzer, who had won his four previous starts, allowed no runs on three hits in the first five innings.

"I really ran my pitch count up. They grinded me apart. They know what I have," Scherzer said of the Phillies. But the Nationals have Harper, and that made all of the difference.

NOTES: Washington RHP Stephen Strasburg (15-4, 3.60 ERA), who left his start after 42 pitches Wednesday, told reporters Saturday he does not know if he will be able to return this season. "It was about as good of news as you can get," Strasburg said when he learned he had a flexor mass strain. "So I'm just trying to take it one day at a time now and do everything I can to get out there, not only as fast as possible but feeling right at the same time." He signed a seven-year contract extension in May; he had Tommy John surgery in 2010.