Gilmore, who will be missing his second consecutive game, was one of four starters to be downgraded to out for the Patriots' Monday Night Football contest. According to the team's official injury report, defensive lineman Lawrence Guy (elbow/shoulder/knee), linebacker Ja'Whaun Bentley (groin) and receiver N'Keal Harry (concussion) also will be out.
Gilmore, Guy and Bentley were initially listed as questionable for the Patriots (2-5), who are in the midst of their first four-game losing streak since 2002. They were among 17 players listed as questionable to suit up against the Jets.
In Gilmore's absence, the Patriots are expected to start J.C. Jackson at cornerback. He has recorded a team-best four interceptions this season.
Carl Davis, who was signed off the Jacksonville Jaguars' practice squad about two weeks ago, could help fill Guy's spot on the defensive line. Rookie Josh Uche is projected to replace Bentley at linebacker.
In six games this season, Gilmore -- the reigning NFL Defensive Player of the Year -- has notched 20 total tackles, one interception, two passes defensed and a forced fumble.