The Jets placed safety Marcus Gilchrist and right tackle Breno Giacomini on season-ending injured reserve on Tuesday.
The team also announced it had promoted safety Ronald Martin and offensive lineman Craig Watts from the practice squad. Guard Martin Wallace was also signed to the practice squad.
Gilchrist tore the patellar tendon in his right knee on the opening kickoff of the second half of the Jets' win at San Francisco on Sunday. He is tied for the team lead with two interceptions and is largely considered the quarterback of Todd Bowles' secondary.
Giacomini played in five games this season after starting the season on the physically unable to perform list with a back injury. He was dealing with back, shoulder and calf ailments, and was inactive at San Francisco.
"He wasn't responding well to treatment," Bowles said. "It was getting worse, so we just shut him down."
Bowles said Giacomini's shoulder was sore, but the back was the main issue. The coach added that Giacomini probably will need surgery on his back. Last week, Giacomini said his back was feeling better, but his calf was giving him the most trouble.
Martin and Watts have spent the entire season on the Jets' practice squad after participating in training camp with New York.
Martin played in eight games for New York last season after the Jets claimed him off waivers from Seattle.
Watts spent his first two NFL seasons with San Diego, and played the second-most snaps among offensive lineman for New York during the preseason.
Wallace, a former Temple standout, has previously been with Cleveland, Carolina, Tampa Bay, Chicago and Arizona.