While the joke around the Watt brothers, T.J. and J.J, is that they just out-work and out-grit everybody, it has to be accepted that these two are generational athletes. Watt was drafted in the first round because he tested off of the charts compared to others in terms of athletic ability.
At the NFL combine, he tested in the 80th percentile or much better than past participants in essentially every athletic drill.
The NFL scouting report of Watt was simple. He was a freak athlete. He has the last name that brings a strong reputation. However, he is a player who only spent one season at Wisconsin as a linebacker. He was still raw in the position, and to defense as a whole, being a former tight end at Wisconsin. That is why it has been so surprising Watt already is where he is as a player.
Still, even as Watt shows that he has those rookie lapses, the Steelers drafted him for his athleticism, and that has bailed him out of situations already.
Below, we see Watt get sucked in by the play action. He is a rookie, it is a run first team, they sell with a pull, it is smart for the Titans to test this matchup. However, as number 81, Jonnu Smith runs by Watt, Watt takes note that it is a pass and rushes back. This is where that speed and athleticism come into play. Watt is about four yards behind Smith when he finally gets turned around. When he dives, he is about three yards behind him. Still, he extends and tips the ball away, making an incredible play off of what could have been charged for a blown coverage.
This is what Watt brings. You can teach him when to stay home and to follow the tight end rather than play in the back field. However, you cannot teach all 250 yard pass rushers to catch up from nearly five yards behind and make a play on the ball.
The ceiling is really high for Watt, and as he works out the kinks, he should solidify himself as an elite player sooner than later.