PHILADELPHIA -- Left-hander Scott Olsen pitched his best game of the season, helping the Nationals defeat the Phillies, 4-1, at Citizens Bank Park on Wednesday night to salvage the three-game series finale.

Olsen pitched 5 2/3 innings and gave up one run on six hits. His only blemish was a solo home run by Shane Victorino in the first inning. After that, Olsen showed that his velocity was back, striking out six of the next seven batters he faced.

"He pitched a very good ballgame," manager Manny Acta said. "He was pounding the zone earlier in the game. The second time around, he pitched behind a little bit, but he made pitches when he had to.

"He didn't back down. That was a good example there that he was determined to pound the strike zone and not giving in to hitters and give up home runs with guys on base."

Olsen was able to gets outs with his slider. Later in the game, Olsen had to adjust and throw more fastballs.

"We were able to get a nice little groove there," Olsen said. "Then they did a real good job to take the slider. They made a real good adjustment -- the whole team. So we had to counter-adjust to them."

The Phillies started to adjust to Olsen in the fourth inning. With one out, Philadelphia had the bases loaded with one out. After Pedro Feliz popped up for the second out, it was third baseman Ryan Zimmerman who made the play of the game.

Chris Coste grounded the ball near the third-base line. Zimmerman dove, backhanded the ball and, realizing he had no chance to get the force at third, threw to first baseman Nick Johnson for the final out.

"In my mind, it was game-saving play," Olsen said.

Said Zimmerman about the play, "He didn't hit it quite hard enough to where I could just tag third. I had to throw it all the way across. I just have to be ready all the time. To get out of that inning without any runs -- Scott had thrown so well. ... Scott had a good outpitch that made people swing and miss. I was just happy to do something to help him."

The Nationals gave Olsen the lead in the sixth off Phillies right-hander Brett Myers. With the score tied at 1, Elijah Dukes singled to center to drive in Zimmerman, who had doubled to extend his hitting streak to a club-record 18 games. Three batters later, Anderson Hernandez singled to right to score Dukes.

Washington added another run when Hernandez doubled in Willie Harris in the eighth. Hernandez went 3-for-4 to raise his batting average to .304.

"He is having quality at-bats. He looks very confident," Acta said. "That why we like him [batting eighth] because he doesn't have any pressure."

It was up the bullpen to get the job done. It was just this past Monday when it blew a four-lead to give the Phillies a 13-11 victory. Acta decided to make changes to the bullpen.

Righty Joel Hanrahan was out as the closer. Acta decided to make veterans Kip Wells and Julian Tavarez part of his bullpen-by-committee. Both Wells and Tavarez did the job, as well as Garrett Mock, who had lost his eighth-inning role. They pitched a combined 3 1/3 scoreless innings.

"Any win we can get at this point is a good win. Getting a lead and holding a lead is a good thing," Wells said.

Tavarez earned his first save since May 28, 2006, when he pitched for the Red Sox. He declined to see himself as a closer because he is confident that Hanrahan will get his job back.

"I don't even think about a save. I know we got a win," Tavarez said. "I'm not going to put into my head that I'm going to be the closer for the year. Hanrahan is going to get his job back. He has real good stuff to close. He made the wrong pitch at the wrong time. I know he will be the closer."

With the victory, the Nationals improved to 5-15. They headed home to Washington to open a four-game series against the Cardinals on Thursday at Nationals Park.

"It's nice to win on getaway day. We'll take this one," Acta said. "That's how the game works. We had a four-run lead the other day and couldn't do it. Today, we won, 4-1. We'll enjoy this one for 30 minutes and then get ready for [Thursday]."