Coach Adam Gase, who confirmed the injury Wednesday, wouldn't comment on whether it is career-threatening. He also said it's too soon to say if Enunwa, 27, who sat out the 2017 season, will need surgery.
Enunwa is scheduled to have further tests on Monday, a source said. Those tests will determine the course of action. Two years ago, he suffered a herniated disk in a training-camp practice. The preliminary indication is the injuries are similar. He was hurt in Sunday's loss to the Buffalo Bills.
"The way he plays, everything is violent," Gase said. "He gives everything he has. I feel for him in the aspect that he's going through something like this. It's not something that's easy for guys that have been doing this their whole life."
Gase said he learned of the severity late Monday, which prompted the team to reach out to the New England Patriots. The Jets traded a 2021 sixth-round pick for wide receiver Demaryius Thomas, who passed his physical and is expected to play Monday night against the Cleveland Browns.
The injury raises questions about Enunwa's future.
The Jets saw him as a key player and rewarded him with a four-year, $33.4 million contract last December, signing him before he became an unrestricted free agent in March. The deal included a $9 million signing bonus, with a $1 million guarantee in base pay for 2019.
The Jets will have to make a decision on Enunwa by the fifth day of the 2020 league year. That's when his $6 million salary for 2020, currently guaranteed for injury only, becomes fully guaranteed.
"He does a lot of the dirty work that nobody really notices," Gase said. "There are some of those things we won't be able to do without him."
Enunwa got hurt early in the first half on Sunday, but stayed on the sideline only briefly. He wound up playing 62 of 67 offensive snaps, finishing with only one catch. He "didn't feel right after the game," according to Gase. During the game, Gase "didn't think anything of it because it's, like, football."
Enunwa has battled injuries throughout his career, but he's a key piece on offense because of his yards-after-catch ability. He was used last season mainly as a possession receiver, but there was talk of expanding his role this year under the new coaching staff. In five seasons, he has 119 catches, 1,617 yards and five touchdowns.
Without Enunwa, the Jets are down two of their top four pass receivers. Tight end Chris Herndon still has three games remaining on a suspension for violating the league's substance-abuse policy.
"He's not 24 anymore; I'm not stupid in that aspect," Gase said of Thomas, 31, who suffered a torn Achilles tendon last December. "I understand there's an aging process here, but he's a big man who can run really well for a guy his size."
In other injury developments, Gase expressed optimism that linebacker C.J. Mosley (groin) and defensive tackle Quinnen Williams (ankle) will play Monday night. Quarterback Sam Darnold was sent home with strep throat, but he is expected to play.