Per the beat writers, the New York Jets have hired Steve Hagen as the new tight ends coach. He will replace Mike Devlin, who has moved to the offensive line. Hagen comes from Cleveland, where he held the same position with the Browns. As you can see here, Hagen has a long history as an assistant spanning back to 1979. Interestingly, he has experience with quarterbacks and running offenses as a whole. Here is another interesting article about Hagen's long and winding history in football. Most notably, Hagen aided in the development of tight ends Benjamin Watson and Evan Moore, both of whom have had their most successful years under his tutelage.
Hagen certainly has his work cut out for him. He's inheriting Jeff Cumberland, an athletic talent that hasn't quite developed yet, and Hayden Smith, the ex-rugby star that's a work-in-progress, but showed some development towards the end of the season. It's unclear if Dustin Keller will be returning next year, although the odds are against it.
By my count, that's a new defensive coordinator, defensive backs coach, offensive coordinator, quarterbacks coach, offensive line coach, tight ends coach, and special teams coach. That's a lot of overhaul, including all three coordinators. Not including their assistants, the only position remaining is the linebackers coach.