Dominating tight ends are becoming less of a luxury and more of a need for strong college programs. A tight end who stretches the field in the passing game always adds to the potency of an offensive attack.
The ideal tight end prospect is an all-around guy who can go deep, force teams into mismatches and make defenses account for him in both the run and passing game. Much like the fullback position, if the tight end is one-dimensional, it forces the offense to be more predictable, and defenses will respond accordingly.
If you can't find a prospect with ideal speed, he must be smart and have a great feel for the passing game and the savvy and work ethic to get it done as an interior blocker. These tight end prospects don't necessarily stretch a defense in the vertical passing game, but they know how to get open, use their bodies well to shield defenders from the ball and find the open seams in the defense especially on third down.
Many high school wide receiver prospects enter college with great athleticism, but lack overall speed or gain a significant amount of weight, forcing them to move to tight end. The same holds true with less athletic tight ends entering college, and many of those players will make the move to offensive tackle.