The Seattle Seahawks head into Week 16 with a crucial game against the Los Angeles Rams that could decide the competitive NFC West race.

But they might have to face the Rams and the San Francisco 49ers in their regular season finale without one of their running backs.

Rookie DeeJay Dallas suffered a Grade 3 ankle sprain that will likely cause him to miss multiple weeks, according to NFL Network’s Ian Rapoport.

Dallas suffered the injury on a kick-off in the second quarter in Seattle’s 20-15 win over the Washington Football Team on Sunday and was carted off with an air cast on his right leg, according to NBC Sports.

The 22-year old running back, who played for the Miami Hurricanes, played 12 games for head coach Pete Carroll and has rushed for 108 yards on 34 carries with two rushing touchdowns while adding 111 receiving yards on 17 receptions and one receiving touchdown. Dallas, however, has not found the end zone since the Seahawks’ 44-34 loss to the Buffalo Bills in Week 9.

While the loss of Dallas will be felt by their rushing attack that averages 125.4 yards per game (11th in the NFL), the Seahawks will have running back Rashaad Penny to fill in the void. The 24-year old Penny returned to the lineup against Washington for his first game this season, finishing with two carries and six rushing yards.

Last season, Penny played 10 games for the Seahawks, finishing with 370 rushing yards on 65 carries with three rushing touchdowns and 83 receiving yards on eight receptions with one receiving touchdown.

With Dallas out for multiple weeks, the Seattle offense will rely more on Penny as they try to secure the division title.