Johnson, the team's most accomplished corner, apparently was injured on a long interception return. He came out after that play and never returned to practice.
Afterward, coach Adam Gase sounded concerned.
"Anytime a guy that makes a living running has a hamstring ... we'll see how it goes," he said. "He's going to have to get a lot of treatment and strengthen it up, and we'll get him back as fast as possible."
The Jets have a major issue at cornerback. Their top three are Darryl Roberts (11 career starts), Atlanta Falcons cast-off Brian Poole and rookie Kyron Brown, an undrafted free agent from Akron. No other corner on the roster has significant NFL experience.
General manager Joe Douglas is scouring the league with the hope of adding veteran help.
Gase said he's counting on defensive coordinator Gregg Williams to scheme up ways to camouflage the lack of experience, but that may be asking a bit much.
"The good thing is, with an experienced defensive coordinator like we have with Gregg, Gregg knows how to get guys into a rhythm, find out what they do well and adapt his scheme to our personnel," Gase said.
Johnson missed five games last season with a quadriceps injury that also occurred in practice. Overall, it was a disappointing year for Johnson, who signed one of the biggest free-agent deals in franchise history -- five years, $73 million.
The Jets are counting on a rebound, especially under Williams. Johnson enjoyed his best seasons with the Los Angeles Rams when Williams was the defensive coordinator. The Rams used their franchise tag on him in 2016 and 2017 before letting him hit the free-agent market in 2018.
It wasn't all bad news Sunday for the secondary. Free safety Marcus Maye, battling a nerve issue in his surgically repaired shoulder, was activated from the physically-unable-to-perform list. He was limited in practicing, participating only in the 7-on-7 period. They will bring him along slowly, hoping to get him ready for Week 1.
In other injury news, right guard Brian Winters is listed as week-to-week after injuring his shoulder in the first preseason game. The expectation is that he will be ready for Week 1. Defensive end Leonard Williams also remained on the sideline with a hip injury.
"We're going to be slow with that," Gase said.