Quinnen Williams has proven a lot to the Jets behind the scenes.

After missing two games since he left the season opener with an ankle injury that was supposed to keep him out for much longer than it actually did, Williams is beginning to come into his own.

This year’s third-overall pick out of Alabama was back in the lineup by Week 5 (after the bye) and showed encouraging flashes of difference-making plays in Week 6, when the Jets took their first win of the season, 24-22 over the Cowboys. The 21-year-old Williams made his presence known.

“He’s been very good. That’s not an easy injury to come back from,” defensive coordinator Gregg Williams said following practice Friday. “There have been a lot of players that I have coached with that injury, that take the full six to eight weeks. They get their little tissues and they want to take the whole time off and that kind of stuff.

“It was very important for Quinnen to show everybody how tough he was and to come back that fast. That elevated his stock in the room around everybody else. They’re all looking at him like, ‘Woah, he’s pretty tough.’ ”

The Cowboys, trailing the Jets 7-3 just before halftime this past Sunday, aggressively kept their offense on the field on a fourth-and-2 instead of going for the field goal. Dak Prescott went to run it to his left, only to be denied by Williams, who took him down to force the turnover on downs.

It was a turning point in the game. Sam Darnold connected with Robby Anderson for a 92-yard touchdown shortly after that to extend the Jets’ lead.

Williams has combined for 11 tackles and five solo tackles through the past two games after not recording a stat in his NFL debut. But Williams is probably his own biggest critic, stating he feels the need to work on all aspects of his game.

“I evaluate myself hard,” Williams told The Post after practice Friday. “Just knowing the things I have to work on, the things I need to improve on. [I need to] chase out my weaknesses on camera, chase out my weakness in myself. Doing that is one of my main goals.”

The defensive front seven has had a few setbacks due to injury, headlined by linebacker C.J. Mosley battling back from a groin injury he sustained in Week 1 and linebacker Neville Hewitt missing all of practice this week with neck and knee injuries. That has forced players like Blake Cashman and Harvey Langi, along with Williams, to assume bigger defensive roles.

“He’s definitely made his presence felt,” defensive end Leonard Williams said of Quinnen. “He came back fast, came back healthy and he’s fly around. He doesn’t mess up often. I think he just feels comfortable and that’s important to have.”

Williams didn’t participate in the Jets’ first meeting with New England in Week 3, but he has a unique perspective on the Patriots after playing for a college football powerhouse.

“You don’t play for [Alabama coach] Nick Saban and be soft,” Gregg Williams said.

“[The Patriots] do everything right,” Quinnen Williams said. “They be where they’re supposed to be every play and they run everything full speed. I played for Alabama. It’s similar to watch those guys and watch other NFL teams and you see the difference. It’s like when you watch Alabama and see other college teams, it’s different just because Alabama does everything right. Alabama set a standard.

“But we have the same thing on this defense on this team. That we’re going to do everything right, we’re going to execute everything right when we’re on the field. We’re going to play every play right.”