The Patriots have always had two classes of tight ends. There is the traditional “Y,” whose job requirements read: 6 feet 5 inches or taller, at least 255 pounds, can run but absolutely must be a standout blocker. He has to be a viable receiver, but not a great one. The “F” or flex tight end is 6-3 or taller, around 235 pounds, must be able to run and be an excellent pass receiver. Does not need to be a good blocker. Everyone in the building agreed that Aaron Hernandez out of the University of Florida, where he did a little bit of everything, was the prototype “F.” There was disagreement on the Y. Some were scared off by Rob Gronkowski’s back surgery in college. There also wasn’t agreement on whether Gronkowski as a rookie could think quick enough to play with Brady. But at least one person did have Gronkowski ranked as the No. 1 Y: Belichick.