Outside of QB, what is the most difficult position to play in football? 

I say it's the safety position because of recognizing run or pass at the snap, cover, open field tackles, last resort 

Or...

Offensive line-Hitting on every snap, assignments, technique

WR-Routes, catching in traffic, blocking, speed 

RB-hits that are given (i say given because Elliot delivers the blow) blocking, creating something out of nothing

Linebacker- run support and getting the flat in coverage, hits, mental, leadership of D

Kicker- pressure, precision, staying loose and ready on sidelines

Looking forward to the responses