The Jets announced later Tuesday that Clark has spinal-cord contusion and will be kept in the hospital overnight for observation. The team said he is expected to make a full recovery.
Clark's father, Al Clark, told ESPN that his son "couldn't feel his legs" initially, but that the feeling came back in the ambulance once he was stabilized.
"Everything seems to be good," said Al Clark, who has spoken with Cameron.
Cameron Clark, a second-year player from Charlotte University, was motionless for several minutes after going to the ground during an 11-on-11 period.
Medical personnel rushed to him and quickly placed the 6-foot-4, 308-pound lineman on a spine board. He was carted off the field to a waiting ambulance. Seventeen minutes after the injury occurred, Clark was transported to Morristown Medical Center.
Coach Robert Saleh didn't provide details, saying the club wants to await further evaluation before releasing information. He said Clark had "some" movement in his extremities.
Asked his level of concern, Saleh said, "I'm an optimist. God willing, everything is going to be just fine, but we'll wait for the evaluation."
Saleh halted practice early as the field got quiet, with players and medical personnel gathered around Clark. It wasn't a public practice, but there were about 200 fans in attendance. The team orthopedist on the scene was Elliott Hershman, a team doctor in 1992 when the late Dennis Byrd broke his neck in a game against the Kansas City Chiefs.
"It's a scary situation when someone gets carted off the field," quarterback Zach Wilson said. "Just praying that he's going to be all right."
Clark, 23, a 2020 fourth-round draft pick, didn't see any regular-season action as a rookie. The organization called it a developmental year for Clark, who was slowed by a shoulder injury. This season, he went into training camp as a backup, fighting for a roster spot.
Saleh said he wasn't sure how the injury occurred.
"I caught it out of the corner of my eye," he said. "It looked like he was kicking [out] in pass protection and then he was on the ground.
"It's never good because football goes away at that moment. It's about the person, his family, everyone in his life. That's what takes precedence at that moment. Football just goes away."