Ray Durham got the Game 4 start at second base against Phillies right-hander Joe Blanton.
Weeks will require surgery to repair a flap tear of his meniscus, the same injury that sidelined Brewers catching prospect Lou Palmisano for most of the 2008 season. The Brewers have not yet scheduled Weeks' surgery, and assistant general manager Gord Ash would not rule out Weeks for a possible berth in the World Series.
Brewers officials waited until about 10:30 a.m. CT to finalize the decision, 90 minutes before Jeff Suppan's first pitch in Game 4.
"The dilemma we were facing earlier this morning was we didn't know necessarily if it was surgical," Ash said. "But the MRI confirmed the tear, so he's done."
Weeks, who was on the disabled list in June after spraining the same knee while trying to turn a double play in Colorado, was hurt in the third inning of Game 3. Weeks hit a ground ball to Phillies third baseman Pedro Feliz, who made a nice stop and then threw to first for the first out of the inning.
"My back leg kind of skipped the dirt, and it put pressure on the outside of my left knee," Weeks said Saturday night.
Head team physician William Raasch examined Weeks after the game and was concerned about the meniscus. Another exam Sunday morning amplified those concerns, so Weeks was sent for an MRI that confirmed the tear.
In the NLDS, Weeks was hitless in four at-bats. Escobar appeared in nine games in September, going 2-for-4 and scoring two runs. He spent the rest of the year at Double-A Huntsville, hitting .328 with 95 runs scored, eight home runs, 76 RBIs and 34 stolen bases. He is a superior defensive shortstop, but has little experience at second base, Ash said.
Brewers manager Dale Sveum met with the coaching staff Sunday morning to select Escobar as Weeks' replacement. Other choices included right-handed-hitting utility man Joe Dillon and left-handed slugger Russell Branyan, who primarily plays first and third base. Dillon has no health issues, and Branyan's sore back is "better," Ash said, so injuries did not impede either player.
Sveum was not available to reporters after the Brewers announced Weeks' injury. But he told Ash and Melvin that Escobar was the unanimous choice of coaches because of his versatility.
"He can play all the infield positions and while he hasn't played outfield in a game, he's worked out there for most of the last month," Ash said. "He's just a very athletic kid. I guess they feel like they can move him around enough to make him the guy they want to use right now."
The Brewers have four September callups on the 25-man NLDS roster: Escobar, outfielder Tony Gwynn, infielder/outfielder Brad Nelson and left-handed reliever Mitch Stetter.