Quarterbacks beware: Big Cat is ready to pounce.

Leonard Williams, the Jets’ sixth-overall selection in the 2015 draft, finished last season as one of the top rookies in the NFL — and now he says his growing pains are over.

“It is different because last year I just kept thinking, ‘rookie, rookie, rookie,’ but now … I know that I’m a pro now,” Williams said during last week’s training camp. “I know the playbook now, so I don’t have to think as much when I’m out there, I can just play. It’s less pressure now that I’m not a rookie anymore, and I don’t have to have that tag or label on me. It’s just been more comfortable overall this year.”

The 6-foot-5, 302-pound Williams had three sacks, 63 tackles and a team-leading 32 quarterback hits in his first season, and it quickly became evident why he was a steal for the Jets after he slid out of the top few picks in the draft.

“You know, a lot of people think I had a good year last year. I think so too — for my first year — but I feel more comfortable this year, so I just wanna improve,” Williams said. “I think I did really well in the running game last year, so during the offseason I’ve been working on my pass rushing.”

The Jets’ defensive line is in a state of flux, with Muhammad Wilkerson having not yet accepted the team’s franchise player tag, and nose tackle Damon “Snacks” Harrison now wearing Giants blue. If Wilkerson doesn’t sign, coach Todd Bowles likely would elevate Williams into the starting front three with Sheldon Richardson and former Steelers nose tackle Steve McLendon.

“[Bowles] is just the type of guy who just wants to keep moving forward no matter who we have with us, no matter who we have on the team,” Williams said, “and he believes in whoever we have.”

Defensive line coach Pepper Johnson said he believes in Williams, too.

“He learned a lot, and I like what I have,” said Johnson, who won two Super Bowl rings as a Giants linebacker. “He actually matured a lot — not saying he was [immature] when he came in. He came in with a maturity, a professionalism. But he just has taken it to another level.”

Williams’ 811 defensive snaps last season, second-most on the Jets’ defensive line behind Wilkerson’s 941. And now the training wheels are off.

“There’s pressure on you being a rookie especially when you go first round, you know, people have high expectations for you, but I had a pretty good year and I’m looking forward to my second,” Williams said. “It’s just rollin’.”