PHILADELPHIA (Reuters) - A masterful Cliff Lee tossed his third consecutive complete-game shutout to steal top billing as the Philadelphia Phillies earned a 5-0 victory in their heavyweight match-up with the Boston Red Sox on Tuesday.

In a potential World Series preview between two of the top teams in baseball, Lee was once again unstoppable and overshadowed Boston ace Josh Beckett with a two-hit performance that extended his streak of scoreless innings to 32.

The red-hot Lee struck out five and improved his record to 9-5 on the season, though the former Cy Young winner was not ready to celebrate prematurely.

"It's not time to pat myself on the back for anything right now. It's the middle of the season, we've got a lot of work to do and a lot of games to play," Lee told reporters.

"I'm going to continue to focus on my routine and what I need to do for each start. I know that's why I've been successful."

Domonic Brown gave Philadelphia an early 2-0 lead with a home run in the second, and Shane Victorino also belted a two-run homer in the sixth to help seal the win for the Major League-leading Phillies (50-30).

Beckett (6-3) entered the night with the best ERA in the Major Leagues at 1.86, but his mark ballooned to 2.20 after allowing five runs in six innings. He had not pitched since June 15 because of a flu virus.

The Boston (45-33) offense, playing without injured Carl Crawford (hamstring) and benched designated-hitter David Ortiz, did not record a hit against Lee until the sixth.

"When he gets the ball I expect him to pitch like he can," Phillies manager Charlie Manuel said. "You'll see pitchers get into hot streaks and they can go a long time and pitch really good."

Prior to the game, the Phillies announced they had placed closer Ryan Madson on the 15-day disabled list with a bruised right hand retroactive to June 19.

(Writing by Jahmal Corner in Los Angeles; Editing by John O'Brien; To comment on this story email sportsfeedback@thomsonreuters.com)