Coach John Fox and defensive coordinator Vic Fangio aren’t doctors. That’s one of their go-to refrains. But a stethoscope might be useful when it comes to cornerback Kyle Fuller, who hasn’t played after undergoing arthroscopic surgery on his right knee in the preseason.

In their own ways, Fox and Fangio seemed to question Fuller’s heart and desire to return Tuesday.

The Bears have until 3 p.m. Wednesday to activate Fuller from injured reserve. It’s the conclusion of Fuller’s 21-day practice window.

But whether Fuller plays this season, it’s clear he’s on shaky ground with the organization that made him the 14th overall pick in the 2014 draft.

Fuller’s career in Chicago is not exactly at a crossroads; it might have hit a dead end. His long recovery from minor knee surgery conflicts with the culture that Fox and general manager Ryan Pace are building.

The Bears have until March to decide whether to pick up Fuller’s fifth-year option for 2018. But at this point, it’s more likely he’s traded by then.

Fox was asked about Fuller’s “level of want-to.”

“That’s hard to measure,” Fox said. “Looking inside people is not real easy. All we can do as coaches is look at what’s on the field, evaluate and make a decision. It’s all about what’s best for the team.”

Fangio, as he’s known to be, was more direct.

“Anytime a guy’s hurt, there are three stages to getting back to the field,” he said. “One is you’ve got to get medical clearance. Two, the player has to say he’s ready to go and feels confident, and he’s champing at the bit to play.

“And then the coaches get involved and see if he’s better than what the other choices are and if he really is back to being able to play. ‘A’ has happened. ‘B’ hasn’t, so ‘C’ is a non-issue.”

Translation: Fuller’s return is on him.

Fuller was in and out of the locker room, but he told reporters that the team said he couldn’t speak, which is typical for injured players.

Pain and discomfort might remain issues for Fuller. He has struggled to stack good days together. And if that’s the case, putting out bad film isn’t in Fuller’s best interests, especially if he senses that his future with the Bears is in doubt.

Considering that Fuller played through a broken wrist and a hip pointer as a rookie, it’s understandable why his pain tolerance has become an issue.

The rebuilding Bears are looking for certain players with certain traits — toughness, dedication and selflessness, to name a few.

Serious injuries have marred the season, but even “healthy” players are ailing at the moment. As players often say, no one is healthy at this time of year. But plenty have played on. The Bears’ 3-11 record doesn’t matter.

Veteran Tracy Porter is an example. He has been on the injury report since Week 3 because of the same nagging knee injury and hasn’t missed a start.

Rookie cornerback Deiondre’ Hall gets it, too. He said that playing through pain was part of his return from a severely sprained right ankle that cost him eight games.

Fox’s and Fangio’s words might spur Fuller back to action. But even then, two games make for an incomplete evaluation.

“A two-game sample may not always tell the truth,” Fangio said.

The truth is, Fuller has struggled to win over the Bears’ new regime, and his absence has made matters worse. Former GM Phil Emery drafted Fuller, not Pace and Fox. Coaches have called Fuller inconsistent, and teammates have questioned his study habits.

And now Fox and Fangio are openly questioning his will to return from injury.