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.
Dan Morgan would have been an all-timer if not for the injuries. He broke his leg after 11 games his rookie year, had 5 or 6 concussions, partially tore his achilles, and had several other injury issues after having no real injuries in college. He still holds the Miami career tackle record.