CHICAGO (CBS) — Chicago Bears starting running back David Montgomery was carted off the field yesterday with a non-contact injury. He slipped during a hand-off drill with quarterback Mitchell Trubisky. The team initially suspected a knee ligament injury but now believes it’s a strained groin.

Also reported is an initial timetable of two to four weeks for Montgomery’s return.

The Bears are scheduled to open their season on September 13 against the Detroit Lions on the road. Their home opener is September 20 against the New York Giants. Montgomery could return for the Lions game, which is just over two weeks away, though the Giants game seems more likely.

The Bears running back was a third-round pick in 2019. He ran for 889 yards and 6 touchdowns on 242 carries and caught 25 passes during his rookie season. Montgomery averaged only 3.7 yards per carry, though subpar blocking is partly to blame.

He is expected to play a bigger role this season in a backfield that also includes Tarik Cohen but generally lacks depth. Cohen is considered more of a pass-catcher. Montgomery dropped a little weight in the off-season and has appeared quicker on the practice field this year.

The Bears will need that boost on an offense that still faces uncertainty at the quarterback position, with Trubisky and Nick Foles both vying for the starting spot. A strong running game would ease the pressure on a woeful passing game.