It happened Saturday in the Jets' first contact practice, when the first-round draft pick, blocking in a kickoff-return drill, collided with the returner. He didn't finish practice.
Initially, it was termed a head injury. The concussion diagnosis was confirmed after he underwent tests.
"The returner got knocked into him and it kind of hit him just right," coach Rex Ryan said. "It's just one of those things, like one of those heavyweights hitting you in the chin and the lights go out, I guess."
Pryor will enter the NFL's protocol for head injuries, meaning he has to be cleared by a neurologist before he can return.
The Jets drafted Pryor 18th overall, in part, because of his physical style. Ryan called him an "enforcer," comparing him to the late Jack Tatum, one of the NFL's most notorious hitters of the 1970s.
As a safety, Pryor is involved in a lot of high-speed collisions. Ryan said he's not concerned.
"Not really," he said. "I think if a guy had two [concussions] or something like that, maybe it would. You know he's used to big collisions. It never looked like that big a deal, but it certainly is now."
Ryan said he's not sure if Pryor had any previous concussions, but added: "He never had a history of it in college."
Before the injury, Pryor had been seeing a lot of work with the first-team defense. He's expected to be an opening-day starter.
It has been a rough couple of days for the Jets' top two picks. Tight end Jace Amaro didn't finish practice Sunday after hurting his right knee in a seven-on-seven drill, but it's not serious, according to Ryan.
There's no practice Monday, but Amaro, a second-round pick, is expected to practice Tuesday. The Jets are calling it knee tendinitis. Amaro said he "tweaked" a patella tendon, which had been bothering him in recent weeks. He, too, downplayed the injury, saying he'll be ready on Tuesday.