The New England Patriots fear wide receiver Julian Edelman suffered a torn anterior cruciate ligament in Friday's clash with Detroit.
Edelman will undergo further examination of his knee on Saturday after he limped off at the end of an 18-yard reception in the 30-28 win over the Lions in week three of preseason.
Although he made it to the sidelines under his own power, Edelman had to be carted away to the locker room after being looked at by Patriots medics.
"We're all hoping for the best," Patriots quarterback Tom Brady told reporters after the game.
"Hopefully whatever test they have to do comes back positively. We'll try to do our best to kind of lift his spirits if we can and see what happens."
Edelman has been Brady's most reliable receiver over several years and had a career-high 1,106 yards worth of receptions last season.
Any long-term absence would see Chris Hogan, Danny Amendola and Malcolm Mitchell move up the depth chart behind offseason signing Brandin Cooks.
Hogan caught two touchdown passes from Brady in Friday night's win, which saw the Patriots open up a 24-0 lead before winning on two late field goals from Stephen Gostkowski.