Jack was hurt during last Sunday's 37-19 loss to Tennessee and did not practice this week. The Jaguars (0-5) leave for London on Thursday evening. They will play the Dolphins (1-4) at Tottenham Hotspur Stadium at 9:30 a.m. ET.
Jack has started all five games this season and is the Jaguars' leading tackler (36). This will be just the eighth game he has missed in his six-year career. Dakota Allen likely will take Jack's spot at weakside linebacker.
The Jaguars have lost 20 consecutive games dating back to a victory over Indianapolis in the 2020 season opener.