Coach Will Muschamp announced the news immediately after Florida's 65-0 win, saying McGee will have surgery Saturday night.
"I'm so disappointed for him," Muschamp said.
He was injured when Florida right guard Trenton Brown and Eastern Michigan defensive end Deshai Powell rolled onto McGee's left leg.
After leading Virginia in receiving last season as a junior with 43 catches for 395 yards, McGee graduated and transferred to Florida in the spring. He was immediately eligible under NCAA graduate transfer rules.
An NFL prospect at 6-foot-6 and 245 pounds, McGee was expected to play a large role in the Gators' new up-tempo spread offense.
"[He] came in here, and it's very difficult to come into a situation for one year," Muschamp said. "He has done it as well as you could imagine.
"This guy's a total team guy, a tough guy."
In McGee's absence, senior tight end Clay Burton had a career day, catching seven passes for 42 yards. Burton had three career receptions in three seasons before Saturday's game.
"We're more than just football teammates," Burton said afterward. "I feel terrible for him."
Muschamp also said starting left tackle D.J. Humphries is out two to three weeks after chipping a bone in his ankle. No surgery is required.
Florida was plagued by injuries in going 4-8 last season. The Gators suffered 15 season-ending injuries in 2013, including 10 to starters.