If you had taken a survey before the 2016 season of the players the Jets could least afford to lose, there would have been a few candidates. Up near the top would have been left tackle Ryan Clady and center Nick Mangold, two former Pro Bowl players anchoring the offensive line. They were the only Jets Pro Bowl players on the offensive line, and they had no obvious quality replacements.
Also on the offensive side of the ball would have been Ryan Fitzpatrick. He was the only quarterback on the roster who has ever played at an acceptable level in the NFL. Though there were certainly Geno Smith supporters, even his supporters had to admit that his ability to duplicate the level of performance the Jets had gotten from Fitzpatrick in 2015 was more of a theoretical hypothesis than anything based in actual evidence put forth by Geno on the field.
Next on the offense would have been the duet of Brandon Marshall and Eric Decker. Coming into the 2016 season these two were the only credible targets in the passing game, with Quincy Enunwa at the time being more of a promising long shot than an established weapon. The loss of Marshall would have been more devastating than the loss of Decker, but the loss of either, coming into the 2016 season, would have left the Jets dangerously thin at the wide receiver position, with only one credible target.
On defense there weren't a lot of indispensable players. The Jets had three stud defensive linemen, so the loss of any one of them should not have been devastating. The linebackers were not a strength of the Jets. If there was any indispensable linebacker it was long time anchor David Harris. The outside linebackers were four deep, all unproven, and somewhat interchangeable. The other inside linebacker position was two deep with Bruce Carter and Darron Lee. The loss of either one would not be a problem; the loss of both would be.
In the secondary the one indispensable player was Darrelle Revis. The loss of any other cornerback or safety would be something the Jets could cover for, but the loss of Revis, who was still one of the best cornerbacks in the NFL a year ago, would be devastating, as there was nobody on the roster who could come close to covering opposing #1 wide receivers.
Those were the indispensables coming into the 2016 season. Look where the Jets are now. Mangold has been out for several weeks with an ankle injury. Clady is done for the year with a torn rotator cuff. Fitzpatrick has fallen off a cliff with his play, and is now the worst starting quarterback in the NFL. Decker is done for the year with multiple injuries requiring surgery. Harris has been out of the lineup with injuries at times and his level of play has fallen off dramatically. Lee and Carter have both been sidelined with injuries, leaving the Jets to start a practice squad player at inside linebacker and have him play 100% of the snaps. And finally Revis has fallen so far from his former heights that it's questionable at times whether he is even an average NFL cornerback, let alone one of the best in the league.
The indispensables have, almost to a man, fallen victim to injury, age, and ineffectiveness. The resulting collapse of the team should be no surprise. The challenge for 2017 and beyond lies in the fact that the Jets have few obvious answers in how to replace the indispensables. These players are for the most part older and well past their prime. There is little reason to expect bounce back years from many of them. Decker could bounce back strong in 2017, or he could be hobbled most of the year while recovering from multiple surgeries. Lee will almost certainly bounce back strong, but we still aren't sure what the Jets actually have in Darron Lee. The rest of the 2016 indispensables may not even be on the team in 2017, and if they are there aren't a lot of good reasons to expect them to return to their formerly high levels of play. Looking at the roster going forward, how many clearly indispensable players can even be identified on the Jets 2017 roster at this point? I struggle to point to a single one, which in itself tells me a lot about just how dire the Jets position will be heading into the offseason.