Already tossing a complete game against the Nationals on April 13, in which he gave up two runs on six hits, Halladay has thoroughly dominated Washington throughout his career, going 9-1 with a 1.96 ERA.
Throwing the 60th complete game of his career against the Mets on Saturday, the right-hander threw 18 consecutive strikes to start the game and didn't throw a ball until the third inning. With the win, Hallday moved to 4-1 with a 2.14 ERA.
"He attacked the zone and got quick outs," Phillies catcher Dane Sardinha said.
The Nationals will counter with lefty John Lannan, who pitched well in his last start against the Giants, but Washington could only plate one run in support.
Lannan walked Miguel Tejada with the bases loaded in the seventh, to push across the eventual winning run in a 2-1 loss for Washington.
"I just didn't locate that pitch," Lannan said. "That was the game."
With his season plagued by poor run support, Lannan is 2-3 on the season with an ERA of 3.78. In the left-hander's three losses, the Nats have scored five runs.
Needing a starter to match Halladay's efficiency, Lannan may be ready for the task. In all six of his starts, he has thrown five innings or more.
Nationals: Zimmerman makes progress
Taking another step in the right direction, Ryan Zimmerman walked a mile on a treadmill Wednesday, only 24 hours after undergoing arthroscopic surgery to repair his torn abdominal muscle. "Took me about 30 minutes," Zimmerman joked at Citizens Bank Park. "I was flying. "It was a slow mile, but I made it."
Jerry Hairston replaced Rick Ankiel for the second consecutive game in center field, after Ankiel injured his wrist while making a catch on Monday night. "[Ankiel] went through some treatment yesterday, made a little progress, but he did a little more to [the wrist] than we thought," manager Jim Riggleman said. "It's a nagging thing -- he's just not real comfortable going out and taking batting practice."
Phillies: Romero activated from the DL
Left-handed pitcher J.C. Romero was activated from the 15-day disabled list Wednesday with a strained right calf and to make room for him, righty David Herndon was optioned to Triple-A Lehigh Valley. In 11 appearances this season, Herndon allowed 11 runs on 14 hits for a 9.28 ERA. "We like David," Phillies manager Charlie Manuel said. "He's still a big prospect for us. He'll be back."
Catcher Carlos Ruiz took swings in the batting cage before Wednesday's game, but he is likely to rest his back Thursday. He could take batting practice Friday. He said his back has improved, but it remains unclear when he might play next.
Right-hander Roy Oswalt is still on schedule to rejoin the team and throw a bullpen session Thursday. If Oswalt has no issues, he is expected to pitch Saturday.
The Phillies and Indians are the only MLB teams this season yet to reach double digits in losses. Cleveland is 20-8, while the Phillies are 20-9.
Allowing only one run in a complete-game win over the Nats on Tuesday, Cole Hamels became the fourth straight Phillies pitcher to throw at least six innings and allow no more than one run. Wednesday's starter Vance Worley added to the streak by going six innings and giving up one run in a win over the Nationals.