"I'm praying for the best for him," Jets running back Le'Veon Bell said, according to ESPN.com's Rich Cimini. "Obviously, that's a scary injury. I didn't even know he got hurt. That's how tough he is...He didn't tell anybody."
This is the second season-ending neck injury Enunwa has suffered in three years. The wideout missed the entire 2017 campaign with a bulging disc.
Gase told reporters that Enunwa, who played 92 percent of his team's snaps against the Buffalo Bills on Sunday, said he wasn't feeling well after the game ended. Tests done Monday revealed the injury's severity.
Gase would not say whether Enunwa's injury is career-threatening.
Enunwa, 27, signed a four-year, $36 million extension in the offseason. He caught 38 passes for 449 yards and a touchdown in 11 games last year.
Without Enunwa, the Jets may turn to newly acquired Demaryius Thomas to fill his role. New York traded a 2021 sixth-round draft pick to the New England Patriots for the 10-year veteran on Tuesday, presumably to fill Enunwa's spot.
Thomas caught 59 passes for 697 yards and five touchdowns for the Denver Broncos and Houston Texans last season. Unfortunately, he suffered a torn left Achilles in December 2018, ending his year prematurely.
However, Thomas returned healthy this offseason and looked great in the Pats' final preseason game against the New York Giants, catching seven passes for 87 yards and two touchdowns.
He'll likely fill the Jets' void in three-wideout sets alongside Robby Anderson and Jamison Crowder.
New York's next game will be home against the Cleveland Browns on Monday at 8:15 p.m. ET.