Jamison Crowder had been one of the best Jets since the start of training camp, quickly developing a rapport with Sam Darnold.

But he failed to make it through the team’s fifth practice Monday, leaving late in the workout with a left foot injury.

The severity is not known, and how the slot receiver hurt the foot is unclear as well. Before walking off under his own power after getting looked at by a trainer, Crowder was having another strong practice, catching a long touchdown pass from Darnold and frequently getting open.

He was set to undergo an MRI exam and other tests Monday, but the Jets didn’t have an update on his status.

“When a guy goes down, the next guy has to step up,” coach Adam Gase said. “Just keep playing, move some things around, call some different plays, feature other guys. That’s just part of football.”

The Jets are top-heavy at wide receiver, with only three established options in Crowder, Robby Anderson and Quincy Enunwa. Second-year pro Deontay Burnett filled in for Crowder with the first team.

Rookie OLB Jachai Polite was considered a steal by some draft experts, falling all the way to the Jets in the third round. But the former Florida star has yet to show that promise, mostly receiving third-team reps. He admitted he’s still finding his way and adjusting to relying on technique rather than athleticism.

“I’m just working on learning the plays and then time will tell in that part,” Polite said when asked if he could make an impact as an edge pass-rusher, a position the Jets are lacking in.

Polite had 11 sacks, six forced fumbles and 19.5 tackles for loss as a junior at Florida, but a poor showing at the NFL Draft Combine hurt his stock. He’s yet to make an impact so far.

“Getting into real games for him is going to be the thing that, where I think he’ll show up a lot,” Gase said. “We’ll notice him after preseason games where he’ll be that guy that gets a sack or a couple sacks in a preseason game and I think that’s what he needs. That’s only going to help his confidence.”

Gase has yet to evaluate his options at punt returner. He won’t do so until the exhibition season begins. The Jets let All-Pro return specialist Andre Roberts leave in the offseason for the Bills. Gase did say rookie Greg Dortch, an undrafted free agent from Wake Forest, seems to have a “natural feel” for returning punts.

“The biggest thing you’re looking for is just guys catching it,” the coach said. “When you get in the preseason game, that’s telling. I’ve been through training camp practices, you watch a guy who catches every one of them, then you get in a preseason game, [he] can’t catch one, puts them on the ground.”