A blowout victory on Saturday allowed the Phillies to avoid losing four in a row to the Nationals for the first time since the franchise relocated to Washington. One reason the Nats have struggled to string together wins in this series as of late has been the presence of Roy Halladay in Philadelphia's rotation.

Halladay has never lost to the Nationals franchise since it left Canada and he'll try to keep that perfect mark intact this afternoon in the finale of a three-game series at Citizens Bank Park.

Aiming to become the National League's first 16-game winner, Halladay has won all nine of his starts against the Nats since they left Montreal, including each of his six outings since joining the Phillies. The reigning NL Cy Young Award winner hasn't lost to the club since the Expos beat him back on June 28, 2002 and he has a career 2.21 earned run average against the franchise in 15 games.

The 34-year-old Halladay owns three victories in three starts over the Nationals this year, holding them to eight runs over 23 innings, though he did allow solo homers to Michael Morse, Danny Espinosa and Laynce Nix the last time he faced them on May 30.

Halladay, who is 15-4 with a 2.51 ERA this year, won his fourth straight start on Monday at the Dodgers. He went just 6 1/3 innings, but allowed one run on nine hits and two walks in a 5-3 victory. He has won 10 of his past 11 decisions and the Phillies are 14-1 over his last 15 outings.

After dropping Friday's opener, the Phillies returned to their dominating ways in this series with an 11-3 rout that was fueled by four RBI from Ryan Howard and three Nationals errors. Howard hit a two-run homer to help back seven solid innings from Roy Oswalt, who was making his second start since a lengthy stint on the disabled list due to a back injury.

"Any time you get a little bit of help [on offense], you're able to be more aggressive," said Oswalt, who won for the first time since June 12. "I was able to get the first pitch over and make them start swinging early."

Philadelphia won for the 13th time in 15 games and padded its lead over Atlanta for first place in the NL East to 8 1/2 games.

After beating the Phils for the first time in his career last time he faced them, John Lannan took the loss after lasting just three innings. However, six of the seven runs he allowed were unearned.

"They score a lot of runs and you give them extra outs [it] is asking a lot of the pitcher," said Nationals manager Davey Johnson.

Morse and Nix both drove in a run for the Nats, who are 4-5 on a 10-game road trip that ends today.

Washington's wins over the Phillies have come in small and infrequent bunches. The club is 13-37 in the past 50 meetings and has won just four of its last 26 trips to Philadelphia.

The Nationals' Chien-Ming Wang will try to build off his first victory in over two years this afternoon in the finale.

After missing a large chunk of 2009 and all of last year due to injury, Wang picked up his first win since June 28, 2009 at Chicago on Tuesday. Following losses to the Mets and Braves to begin his Nationals career, the right-hander held the Cubs to just one hit and two walks over six scoreless innings of a 3-1 win.

"He was sharp tonight, Everything they hit was on the ground. Just a magnificent performance," Johnson said of his sinkerballer, who carried a no- hitter into the sixth and lowered his season ERA to 3.60 through three starts.

The 31-year-old Wang will be making his first career start against the Phillies, but did face them in relief back on May 22, 2009. He allowed two runs on six hits over three innings.