David Garrard was on Sirius radio and shed some light on his sudden departure from the Jets. It is his knee, not any Jets related QB drama, that will prevent him from playing this season. Garrard is going to retire, his health will prevent him from being part of the QB competition.
The Jets are interested in seeing Garrard in camp though, as an interim coach.
David Garrard said on Sirius that Jets have offered him opportunity to work with the team this summer in some capacity (non playing) #nyj
— Manish Mehta(@MMehtaNYDN) May 16, 2013
Here is a thread with several additional articles and more information on David Garrard.