The Jets defense crumbled without C.J. Mosley, and now it will have to play a full game without the standout middle linebacker against a more talented offense.

Mosley was ruled out of Monday night’s game against the Browns with a groin injury, as was rookie defensive lineman Quinnen Williams (ankle).

Neither practiced this week, leaving the defense shorthanded and coach Adam Gase without his leader on offense (Sam Darnold) and defense (Mosley).

Mosley, the big free-agent acquisition from the Ravens, was having a big opener against the Bills — notching a pick-six, five tackles and two passes defensed — before hurting his groin late in the third quarter. Without him, the Jets allowed the Bills to score 17 unanswered points.

He will be replaced by rookie fifth-round pick Blake Cashman, who had two tackles in the opener after a strong training camp. Mosley’s absence leaves the Jets without their two starting inside linebackers, after Avery Williamson suffered a torn ACL in the second preseason game and was lost for the season.

New WR Demaryius Thomas (hamstring) didn’t practice, but he is being listed as questionable. Gase said this week he didn’t need to see Thomas, who he coached for five years with the Broncos, on the practice field to put him in the game if he was physically able to play. LT Kelvin Beachum (ankle), RB Le’Veon Bell (shoulder), PR Braxton Berrios, G Brian Winters (shoulder), OL Alex Lewis (shoulder) and DL Steve McLendon (hip) were all limited on Saturday and are questionable.

The Browns will be without starting CB Damarious Randall (concussion). He was ruled out on Saturday. So were OT Kendall Lamm (knee), RB Dontrell Hilliard (concussion) and LB Adarius Taylor (ankle).

DL Henry Anderson was fined $10,527 for unnecessary roughness for his hit on Bills QB Josh Allen in last week’s game, according to a source.

— Additional reporting by Brian Costello