First-year coach Dan Campbell confirmed the injury Monday afternoon.
"I'll confirm that. Yes, he does. We'll know a lot more this afternoon as it pertains to how long he's gonna be," Campbell said. "I mean, certainly this will be weeks and weeks and that's if we get him back for the season. But he's out for a significant amount of time, if not the whole season."
He exited during Detroit's final offensive possession of the first half with three catches for 38 yards. Given the Lions' lack of depth and quality at the wide receiver position, this loss is another huge blow to the winless team.
Cephus has the third-most receiving yards (204) on the team with 15 receptions and two touchdowns and was getting better on a weekly basis.
His injury adds to the laundry list of injured players on the Lions' roster, including linebacker Romeo Okwara (Achilles), defensive end Da'Shawn Hand (groin), center Frank Ragnow (toe), offensive tackle Taylor Decker (finger), wide receiver Tyrell Williams (concussion) and cornerbacks Ifeatu Melifonwu (thigh) and Jeff Okudah (Achilles); they are all on the injured reserve list.
There's hope that Decker is among those who can return this week.
"We're gonna see where Decker's at Wednesday," Campbell said. "At least that's where we'll begin."