Whatever factors have contributed to the Philadelphia Phillies tumbling suddenly into mediocrity this season were glaringly absent all weekend, as Cliff Lee‘s seven strong innings powered the Phillies to a 4-1 win over the Washington Nationals Sunday at Citizens Bank Park and a three-game sweep of the current National League East leaders.

Washington saw its lead in the division cut to five games ahead of the Atlanta Braves, who played Sunday night in San Francisco.

The Nationals and Phillies have done a sort of “Freaky Friday” switcheroo this year, as the perennially contending Phillies underperformed under the weight of injuries and aging veterans, while the Nationals, routinely near the bottom of the NL East, burst out in 2012 in an early show of what the front office hopes to be a power for years to come. Yet you wouldn’t know any role reversal had happened at all if you had just started paying attention this weekend. The Nationals were carved up by Philadelphia’s starting pitching, while the Phillies hitters took advantage of the one shaky inning Washington’s starters were generally giving them.

Lee was the latest Philadelphia hurler to climb into the not-so-way-back machine. Somehow entering the game having earned only two wins this season, the 33-year-old left-hander looked to be in his Cy Young prime. One night after Roy Halladay shredded the strike zone, throwing 86 strikes of his 105 pitches, Lee (3-7) was equally as precise, hurling 77 strikes in 99 pitches while making splinters of Washington bats all afternoon.

Jordan Zimmermann began his afternoon trading zeroes with Lee in what appeared to be another nice pitcher’s duel and was getting plenty of help from his defense. Steve Lombardozzi and Jayson Werthboth made nice plays to help Zimmermann (9-8) preserve his end of the scoreless draw, but things came unraveled quickly in the fifth.

Kevin Frandsen led off with a single and went to second on a passed ball by Nationals catcher Jesus Flores. Bryce Harper then saved a run, at least momentarily, with a stellar diving catch in center field to rob Erik Kratz. But Lee, of all people, drove a double over Harper’s head to plate Frandsen and open the scoring. Adding insult to injury, Jimmy Rollins then deposited a 3-1 pitch into the right-field stands for a two-run homer and a 3-0 Philly lead.

Zimmermann was done after five innings, but the Phillies were not. Laynce Nix greeted Tom Gorzelanny rudely with a line-drive home run to right that extended the Philadelphia advantage to 4-0, more than enough the way Lee was throwing, although the Nationals could have made things interesting in the seventh if not for a quirky bounce.

Werth led the inning off with a dribbler back to Lee that the pitcher threw away, putting Werth on second. The next batter, Adam LaRoche, hit a high fly ball to right that appeared to leave the yard, but instead bounced off the top rail in front of the bleachers. Despite the umpires signalling “in play,” both Werth and LaRoche went into home run trots. But instead of a 4-2 game, Werth had to stop at third and LaRoche got caught in a rundown for the inning’s first out. Tyler Moore then underscored the gaffe with his second double of the game, which did score Werth but could have been much more of a hammer blow to Lee.

As has been the case throughout the weekend, the Phillies bullpen, which had not been a strong suit of the club, allowed Washington nothing, with Josh Lindblom throwing 1 2/3 innings of perfect relief Sunday to earn his first career save.

Champ of the Game: Cliff Lee. Lee picked up where Halladay left off Saturday night, allowing seven hits and one run over his seven innings, striking out five while walking none, while also contributing the game’s first RBI. For the Nationals, Tyler Moore gets the nod from a slim list of candidates, the rookie making the most of his increased playing time with two doubles and Washington’s only ribbie.

Chump of the Game: Danny Espinosa‘s 0-for-4 outing in the leadoff spot could have been predicted from the game’s first at-bat, as he went down swinging at three pitches by Lee and looked terrible doing it. For the Phillies, Erik Kratz might have had an RBI if Harper hadn’t robbed him of that hit in the fifth, but instead he just went 0-for-3.

Next Game: After an unscheduled extra night in Philadelphia, the Nationals will travel to Miami hoping any and all tropical disasters have long since passed. The Nats and Marlins start a quick two-game set on Tuesday night at 7:10 ET at Marlins Park. Stephen Strasburg (15-5, 2.85 ERA) will take the mound for Washington against the Fish and Ricky Nolasco (9-12, 5.07)