The guy can coach college football, that is for sure. But can he coach in the NFL? Saban couldn't but Jimmy Johnson did. It took Pete Carroll years to figure it out and Jim Harbaugh had success and troubles in the NFL. Lou Holtz even had a cup of coffee with the Jets.
Urban is used to doing things his own way. He likes to accept and leave jobs on his own terms. When he got suspended at Ohio State, you pretty much could read "The F U" on his face. He left after that season.
Jacksonville has a GM but he is just a figure head.