The Detroit Lions are coming off a tough 48-42 loss to the Buffalo Bills on Sunday, who snapped their 11-game winning streak. The Lions tried to fight back valiantly but it wasn’t enough to keep their winning streak alive.

Despite the loss, Detroit still controls its playoff destiny as they try to lock down the No. 1 seed in the NFC. However, the Lions’ chances to win the top seed took a significant hit on Monday, as they lost one of their key playmakers.

According to ESPN’s Adam Schefter, veteran running back David Montgomery is out indefinitely after suffering an MCL injury in Sunday’s loss to the Bills. Schefter adds that the veteran running back is undergoing additional testing on his knee and getting a second opinion. But Montgomery could be done for the season.

Injuries have hit the Lions hard this season as they have 21 players on injured reserve. Detroit added three new players to the list on Monday, with defenders Carlton Davis, Khalil Dorsey, and Alim McNeil suffering season-ending injuries.

Montgomery only had four yards on five carries and four receptions (four targets) for 31 yards in Sunday’s loss against the Bills. Montgomery and Jahymr Gibbs have played a huge role in the Lions’ success as they are the best RB duo in the league.

Sonic and Knuckles as the duo is famously called have helped the Lions be one of the rushing teams in the league. Detroit is ranked sixth in rushing, averaging 143.7 yards per game.

The 27-year-old Montgomery has been excellent on the ground this season with 775 yards and 12 touchdowns on 185 carries. He’s been utilized in the passing game, posting 36 receptions (38) targets for 341 yards.

If Montgomery is down for the rest of the season, Gibbs will certainly see an uptick in snaps as Detroit’s new leadback. Craig Reynolds and Sione Vaki could see more work too out of the backfield.

However, it will be tough to replace Montgomery’s production as he’s the perfect complement to Gibbs in the backfield. The Lions will look to rebound in Week 16 against the Chicago Bears at Soldier Field.