What player in the NFL, past or present, would you have wanted to see succeed so badly but due to injuries, off the field issues, or whatever happened just derailed their career? For me it was unfortunate to see players like Josh Gordon or Justin Blackmon have their careers end or never getting back on track because of off-field issues.
I think a similar, but not as talented or succesful, example is Mike Brown. He played all 16 games his first 4 years and earned a 1st team all-pro, but played less than 8 games in 3 of his final 6 seasons. He was a thumping safety who had a nose for the ball and made big plays, but it felt like we never really got to see him in his prime.