From PFT, The Real Deal on Daboll..

[DarrylS]

Doesn't seem all that complicated, he wanted something, did not get it, contract he walks down the road to NY.

http://www.profootballtalk.com/rumormill.htm

THE REAL DEAL ON DABOLL

There has been much confusion over the past few days regarding why and how the Jets were able to pilfer Pats assistant coach Brian Daboll, who most recently coached the team's receivers and previously was a defensive assistant.

Per a league source, Daboll wanted to be the quarterbacks coach, and head coach Bill Belichick declined the request.

Coincidentally, Daboll's contract was expired. And so he left

 

[NoCal Patriot]

That makes sense.Sometimes there really is a simple explanation.

 

[MoLewisrocks]

QB's coach does seem to be a stepping stone to OC guruship. Schottenheimer was the QB's coach in SD before he got the JETS OC gig. A quick check on NFL.com doesn't show a QB's coach for the JETS so perhaps Schottenheimer handled that as well as OC last season (as Josh has here) and Eric is willing to bring Brian in to that slot as insurance should Schottenheimer be presumed to be looking to rejoin Dad next season or just highly motivated to seek a HC vacancy in the near future.

Sounds like BB was sending the message that the path upward is blocked here. Which would also be an endorsement of his current HC much to the chagrin of some here.