Denver Broncos safety Rahim Moore had emergency surgery on Monday to repair a lower leg ailment called lateral compartment syndrome, a disease that can lead to amputation if not treated quickly, USA Today reported.
Moore left in the second quarter of Sunday's game against Kansas City and was ruled out at halftime.
Interim Broncos coach Jack Del Rio provided no timetable for Moore's return.
"It's just one of these kind of freakish things that can occur, and it did," Del Rio said. "They got the doctors right on it and he went in and had the surgery. I mean, it can be a very serious injury."
Compartment syndrome typically occurs in victims of traumatic events, such as car accidents or crushing incidents.
Moore did not appear to take any major hit during Sunday's game, although it is a condition that can worsen over time.
"If you get significant trauma to part of the leg and it causes significant swelling, what happens is the swelling of the muscles becomes so great there is nowhere else for it to go," said Dr. Jason Stoneback, the director of orthopedic trauma at University of Colorado Hospital, said according to the USA Today report. "You essentially get ischemia to the muscles in that compartment - or lack of blood flow, and the muscle then dies. You can lose function of those muscles permanently, and it can destroy nerve function, or you could even lose your leg."
Mike Adams replaced Moore and is likely to start in his place. Adams was a starter for most of last season.