Jack sat out last week's game against Tampa Bay with the injury for the first time in his career and did not practice on Wednesday. He had appeared in 59 consecutive games since the Jaguars selected him in the second round in 2016.
Donald Payne, who had just 10 defensive starts prior to starting last week's game in Jack's place, likely will start at middle linebacker for the final four games.
This was a disappointing season for Jack, who signed a four-year extension through 2023 worth $57 million with $33 million guaranteed. Jack will make $14.25 million annually when the extension kicks in, which trails only Bobby Wagner ($18 million) and C.J. Mosley ($17 million) in annual salary among inside linebackers.
He has 66 tackles (just three for loss) and one interception. The Jaguars rank 28th in the NFL in rush defense (136.6 yards per game) and have given up 200-plus yards rushing a franchise-record four times this season.
Jack has started 53 of the 59 games in which he has played, including the last 45 in a row, and has 285 tackles, 5.5 sacks, three fumble recoveries and one interception. He also has 16 tackles, one sack, one interception, and one fumble recovery in three playoff games.