Albert Breer of The MMQB first reported the MRI showed a complete ACL tear in his right knee. Edelman was carted to the locker room in the first quarter after he went down with a non-contact injury while making a cut following a reception from quarterback Tom Brady.
"Great competitor, works hard, tough, does all the things that you ask him to do," Patriots head coach Bill Belichick said Saturday, per Ben Volin of the Boston Globe. "I feel badly for him of course."
ESPN.com's Jeff Darlington reported following Friday's game that Edelman was "not optimistic" about the MRI and believed he tore his ACL.
Brady was asked about Edelman's injury after the Patriots defeated the Lions 30-28, via ESPN.com's Michael Rothstein:
"We'll see what the extent is," Brady said. "We're all hoping for the best. It's tough any time a teammate goes down. We've all been playing long enough where, when someone does, other people have to step in and fill the void.
"Hopefully that's not the case, but, you know, we'll figure it out tomorrow."
Edelman has been with the Patriots his entire career. The 31-year-old has risen from a seventh-round draft pick in 2009 to become one of the most productive receivers in the NFL. He has recorded at least 92 receptions in three of the last four seasons and set a career high with 1,106 receiving yards in 2016.