More on his status will be known Sunday morning.
The Brewers staved off elimination on Saturday night by claiming a 4-1 win over the Phillies in the best-of-five NLDS.
Weeks incurred his injury while trying to beat out a ground ball to third base to lead off the second inning. On the play, Phillies third baseman Pedro Feliz made a nice stop on a short-hop. Weeks charged hard to first but was thrown out.
Just before reaching first base, Weeks felt something, and he then stumbled across the bag. He walked gingerly back to the bench. In the dugout, Weeks tried to shake off his aching leg.
"My back leg kind of skipped the dirt, and it put pressure on the outside of my left knee," Weeks said.
Even if fully healthy, the Brewers wouldn't be starting Weeks on Sunday because Philadelphia is starting right-hander Joe Blanton. Weeks gets the nod against lefties.
"We'll find out a little bit more in the morning how it is," Brewers manager Dale Sveum said. "I don't think it's nothing major right now, but it was a little sore. So we had to get him out of the game."
Weeks went back on the field for the third inning, but wasn't involved in any plays. An inning later, veteran Craig Counsell took over at second base.
"I probably shouldn't have, but I wanted to see how it felt," Weeks said of playing a half-inning more. "I just couldn't go."
He said the knee stiffened on him.
Weeks was placed on the 15-day DL on June 9, retroactive to June 7, with a sprained left knee. He was injured on a take-out slide by Jeff Baker of the Rockies on June 6. He was reinstated on June 22.
He said the discomfort in his knee is similar to how he felt after the collision in June.
"It's pretty much the same thing as in Colorado," Weeks said. "It was pretty much the same thing, the meniscus. I'll know more tomorrow when they test it out."
In the NLDS, Weeks is hitless in four at-bats.
Joe Frisaro is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.