The injury revealed that he had a particular condition that made him more susceptible to neck injuries, so the doctors wouldn't clear him to keep playing because a similarly innocuous hit could paralyze him. If memory serves, it's the same reason Sterling Sharpe retired, plus another promising young WR named Terrence Murphy for the Packers. (That one was again the Panthers too, coincidentally.)
The injury revealed that he had a particular condition that made him more susceptible to neck injuries, so the doctors wouldn't clear him to keep playing because a similarly innocuous hit could paralyze him. If memory serves, it's the same reason Sterling Sharpe retired, plus another promising young WR named Terrence Murphy for the Packers. (That one was again the Panthers too, coincidentally.)