As I said, Gregg's injury opened the door for the lil Gronkster to make the 53. Couple that with an aging Felton and it was Gronk's position to lose. I'm suprised that this is being reported as some kind of a shock. Gronk can play H-back like Gregg, and must develop more upper body to knock away would be tacklers along with using better technique.
The measurable's between Glenn & Rob aren't far off: and Glenn's combine / pro day numbers indicate he's quicker, shiftier and stronger even in the broad jump. Whereas big bro possesses faster straight line speed and greater upper body strength. Glenn has better below the waist metrics which will help him stick around the league for 3-5 seasons as an H-back, utility fullback.