As per Michael Lombardi at The National Football Post this morning:
The Jets have one tight end on the team, and if they can’t move up in the draft and select a quarterback, then tight end is a viable option. And before you email me about the great Dustin Keller, please know this: He can’t block — at all. He is a mismatched wideout who is very effective in the passing game, but he can’t play tight end full time — and if he has to block anyone, the Jets are in trouble. So for the Jets to maximize Keller’s talents, they need another tight end who can line up on the line to be the blocker, the protector and the physical player — all the things Keller will never be successful doing.