Trumaine Johnson had one of his best moments of training camp … and then it became one of his worst.

The Jets cornerback intercepted a Sam Darnold pass intended for tight end Eric Tomlinson and raced to the end zone with it. On that run, though, he felt something in his hamstring and sat out the rest of practice.

It is unclear how long Johnson will be out, but the Jets’ thinnest position just got thinner.

“Anytime a guy that makes a living running has a hamstring [injury] … we’ll kind of see how it goes,” coach Adam Gase said. “He’s going to have to get a lot of treatment and keep strengthening him up and get him back as fast as possible.”

Gase said Johnson would undergo tests on the hamstring later Sunday and he would have more information Monday.

The Jets entered training camp with cornerback as the position they were the most concerned about. They knew they could not afford an injury there. Now, they have one.

With Johnson out, the Jets top three cornerbacks are Darryl Roberts, Brian Poole and Kyron Brown. Roberts has 16 career starts, Poole has 21 and Brown is an undrafted rookie out of Akron. The team just waived Derrick Jones, who had been its fourth corner.

“We’ll just keep rotating guys in there,” Gase said. “We’re just going to keep competing. That’s what we have to do. We need some young guys to step up. They’re going to have to play well.”

The Jets signed Johnson to a five-year, $72.5 million contract before last season. He had an up-and-down first year with the team, including missing five games with a groin injury. The Jets were counting on Johnson having a bounce-back season under defensive coordinator Gregg Williams, who coached him with the Rams.

Now, those plans are on hold.

The situation is reminiscent of 2014 when the Jets suffered a few injuries during training camp at cornerback that left them hurting at the position and it was a problem area all season.

It will be on new general manager Joe Douglas to try to find some answers at the position, but that won’t be easy. Teams don’t let good cornerbacks walk out the door.

For the moment, the Jets are counting on Williams to coach up the young players.

“The good thing is with an experienced defensive coordinator like we have with Gregg,” Gase said, “Gregg knows how to get guys into a rhythm, find out what they do well, adapt his scheme to our personnel. Right now in the preseason, we’re going to challenge our guys. We’re going to play a lot of man. We’re going to do a lot things where it’s hard and one-on-one. You have to see where you’re at with those guys.”

Brown is intriguing. An undrafted free agent, he had a strong spring and moved up the depth chart over the past few weeks to play with the second team. Now, he will be running with the starters and facing the Jets starting receivers.

“The more reps he gets out here, the more times he goes against Quincy [Enunwa] and Robby [Anderson] and [Jamison] Crowder, the better that will be for him,” Gase said.Even though he is from a small school, Gase said Brown has looked like he belongs.

“This is not too big for him,” Gase said. “You see a guy that just keeps competing.”