Initial tests indicate that Kansas City Chiefs running back Isiah Pacheco fractured his fibula in Sunday’s win over the Cincinnati Bengals, NFL Network Insider Ian Rapoport reported Monday, per a source.

Rapoport added that more information needs to become available to determine the severity of the injury, but Pacheco is certain to miss several weeks and a reserve injury is a real possibility.

Pacheco left the game in the fourth quarter, leaving the stadium on a walking boot and crutches. The Chiefs RB had 90 yards on 19 rushing attempts and five catches for 21 yards in the win.

More on this story in the NFL soon.