Thinking about the sad case of Randy Gregory made me remember some of the other Cowboys players over time that were blessed with great talent but had personall issues that seriously damaged their careers and legacies. Here are some that come to mind:
Randy Gregory - we will never know how good he could have been
David Irvin - another pot casualty. Like Gregory we will never know how good he could have been, but he had great talent.
Duane Thomas - Huge talent with an even bigger chip on his shoulder. Didn't get along with anybody - teammates, coaches, media ...
Lance Rentzel - Star player with a beautiful celebrity wife and a predilection for flashing children.
Hollywood Henderson - a LB and one of the fastest players in the NFL. A true athletic freak. Serious cocaine habit derailed his career
Harvey Martin - Had a very good career anyway, but without the multitude of drugs might be discussed alongside guys like Bruce Smith, Deacon Jones etc ...