That injury, Gase admitted Sunday night, played a small factor in why he has decided to sit star running back Le'Veon Bell for the remainder of the preseason. Bell, the team's prized free agent, saw no action in the first two games.
"I was 99.9 percent sure what we were going to do," Gase said, referring to Bell. "The [Williamson injury] probably made it 100."
It's rare for coaches to question themselves publicly, but Gase seemed remorseful about how he handled the Williamson situation.
Williamson, their leading tackler last season, played late into the second quarter, the only starter on the field at the time when he suffered a torn ACL. It happened when cornerback Tevaughn Campbell dived into Williamson's right knee when trying to defend a pass in the end zone.
After the game, Gase gave a cryptic explanation, saying players were designated for a specific number of snaps. Three days later, meeting reporters for the first time since the game and knowing the full extent of the injury, he struck a different tone.
Asked if he regrets the decision to play Williamson with the backups, Gase said, "Yes, I do."
He went on to say Williamson was learning a new position -- weakside inside linebacker -- and that the coaches wanted him to play alongside Neville Hewitt, the backup middle linebacker. Basically, they were trying different combinations to prepare themselves in the event of an injury to starting middle linebacker C.J. Mosley.
"Looking back on it -- hindsight is 20/20 -- I wish I would've gotten him out of there a series earlier," Gase said. "I talked to him. It's on me. I'm the one who has to make that call and get him out of there. We didn't. It's a shame because he was having a good camp."
Williamson, who signed a three-year, $22.5 million contract in 2018, has a fully guaranteed salary of $6.5 million. But the injury increases the chances of him being released next season, when there are no guarantees left in the contract.
Gase, who had been secretive with regard to his weekly plan for Bell, was surprisingly candid after the team's annual Green & White practice at MetLife Stadium. The Jets play the New Orleans Saints on Saturday night at MetLife. Before the first two games, Gase refused to divulge his Bell plan until kickoff.
"He's in a good place right now," Gase said. "The way he's working in practice, the way he's running the ball in practice, I feel really good about him when he hits the regular season."
Bell, who wasn't available to reporters, has said he would leave it up to the coaches. Bell seemed fine with the decision on Twitter.
Bell's practice reps have increased in recent days. After sitting out last season in a contract dispute with the Pittsburgh Steelers, he hasn't played a game in 19 months.
"I feel like he's in great shape," Gase said. "He's been contacting about as good as anybody on the practice field, so I feel confident he'll be ready for Week 1."
Meanwhile, recently signed center Ryan Kalil made his practice debut. Kalil, 34, who ended a short-lived retirement by signing a one-year, $8.4 million contract on Aug. 1, admitted he needs a lot of work before Week 1. He misfired on two shotgun snaps.
"Not rusty, just playing slow," he said. "Physically, I feel like I'm in good shape. Football shape, not so much."
Darlington: Williamson's ACL injury another blow to the Jets
Jeff Darlington, John Fox and Jack Del Rio react to Jets LB Avery Williamson tearing an ACL and detail the next steps for the organization.