The Chicago Bears will be without running back David Montgomery for four to five weeks, according to ESPN's Dan Graziano.

Graziano reports that Montgomery has been diagnosed with a knee sprain after exiting Sunday's 24-14 win over the Detroit Lions.

The 24-year-old grabbed his knee after a five-yard rush in the fourth quarter and was helped off the field.

"As soon as he got tackled and I saw his facial expression and heard him, I was waving my hand for the trainers to come over as fast as they can," Bears receiver Darnell Mooney said.

Montgomery played a major role as the Bears improved to 2-2, posting 106 rushing yards and two touchdowns prior to the injury against the Lions.

On the season, Montgomery leads the Bears with 309 rushing yards and three touchdowns.

The Bears will visit the Las Vegas Raiders on Sunday, before hosting the Green Bay Packers in Week 6 and then facing the Tampa Bay Buccaneers in Week 7.