There was a palpable feeling last night at sold-out Citizens Bank Park that the anticipation for October has officially begun.

The Phillies started the evening with a seven-game lead in the NL East with 20 games remaining, and the first contest of a three-game series against the worst team in the big leagues promised that their comfortable advantage was in no danger any time soon.

So it's a good time for the Phillies to tend to some matters with the postseason in mind. Such as: Is there anything the matter with Cliff Lee, who had raised concerns because he was banged around in his three previous starts?

Lee calmly soothed those worries with a 5-0 shutout of the Washington Nationals. He allowed six hits and struck out nine, and afterward explained that the main reason he gave up 16 earned runs in his three previous starts was that he didn't mix his pitches enough.

"I think my past few outings, I got a little fastball-happy and obviously gave up hits and runs because of that," the lefthander said after raising his record to 7-2 with the Phillies and 14-11 overall. "So I tried to be more conscious of mixing speeds, and it seemed to work. That's the name of the game. You've got to mix speeds. You've got to mix location and be as unpredictable as possible. For me, throwing my curveball and slider was a big part of that."

Lee has three complete games in his nine starts for the Phils. And for one night, he spared the season's 64th sellout crowd from any bullpen drama.

Manager Charlie Manuel said he never considered taking out Lee, who threw 124 pitches as the Phillies got their second straight shutout win.

Before the game, Manuel said he was well aware that Lee had pitched 207 innings, ranking sixth in the big leagues. He was on the alert for signs of fatigue, but he saw none last night.

"At the end, he showed he was strong the way he was popping his fastball," Manuel said. "It had some good life on it."

The Phillies had seen two distinct versions of Lee after they acquired him from Cleveland in a six-player deal in late July.

There was the version that earned him the American League Cy Young Award last season, when he went 22-3 for the Indians. Lee won his first five starts for the Phils with remarkable precision, allowing only 24 hits in 40 innings with a 0.68 ERA.

The other version of Lee was quite different. In his previous three starts, he went 1-2 with a 9.60 ERA.

Lee had an unusual fourth inning, especially by his standards. A hallmark of his game is his pinpoint control, yet he walked three batters after not allowing a walk in his previous five starts. It prompted a visit to the mound by pitching coach Rich Dubee before Lee struck out Josh Bard to end the threat.

Manuel thought Lee was getting squeezed by home-plate umpire Joe West.

"I felt like in that inning he should have had some pitches, but I guess Joe didn't see it that way," Manuel said.

Lee got all he would need in the first inning on a run-scoring single by Chase Utley before his comfort zone was expanded by a four-run second inning that made it 5-0.

Carlos Ruiz had the game's biggest hit, a bases-loaded double that scored three runs in the four-run fourth. Ruiz had another double and narrowly missed hitting homers his other two at-bats. It was his fourth game this season in which he drove in three runs.

The catcher is batting .371 (26 for 70) with 16 RBIs since Aug. 15.

"He's seeing the ball good," Manuel said. "He's being more aggressive at the plate. He's more selective. That was a big hit. It gave us some cushion. We didn't do anything after that."

Although he didn't need much help, Lee was aided by some sloppy baserunning by the Nationals.

In an example of how the dreadful Nats can't get out of their own way, their third inning ended when a hard grounder by Justin Maxwell hit teammate Alberto Gonzalez as he was running to third base.

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The Phillies Zone, at http://go.philly.com/sports.

Contact staff writer Ray Parrillo at 215-854-2743 or rparrillo@phillynews.com.