Steelers' Ben Roethlisberger sprains MCL in knee, out 4-6 weeks

Steelers quarterback Ben Roethlisbergersuffered a sprained MCL in his left knee midway through the third quarter of Sunday's 12-6 win over the hostSt. Louis Ramsand will miss four to six weeks as he recovers, a source has told ESPN senior NFL analyst Chris Mortensen.

The injury did not include a tear of the ACL in the knee, the source said.

Steelers coach Mike Tomlin said the team will provide an update Monday.

With 5:35 left in the third quarter, Rams safety Mark Barron sacked Roethlisberger after coming on a blitz, hitting him just below his left knee. Roethlisberger went down and immediately grabbed at the knee before the play was whistled dead.

Roethlisberger reached the sideline with some help but was immediately taken to the locker room on a cart. Michael Vick replaced Roethlisberger at quarterback.

"I thought it was kind of low," Steelers offensive lineman Ramon Foster said of the hit. "I think the NFL will look at it."

Conversely, when asked if he had a problem with the hit, Tomlin responded, "I didn't."

Barron said he tripped over someone's feet en route to Roethlisberger.

"I stumbled a bit but on my way down I caught a piece of his leg," Barron explained. "I'm not sure exactly what area it was but that's what happened."

Before the injury, Roethlisberger was 20-of-24 for 192 yards with an interception,while Vick finished 5-of-6 for 38 yards.

Information from ESPN Staff Writer Nick Wagoner was used in this report.