Badgered by a chronic hip injury last season, Harvin first pondered calling it quits when the Bills placed him on injured reserve last November.
"It was about me taking time off to heal," Harvin said of his retirement Tuesday. "Knew the level I wanted to play at and couldn't then. I'm refreshed and I'm ready to go."
"Percy is a guy that worked so hard," said coach Rex Ryan, via the team site. "It's either full speed (or nothing), and sometimes you try to back him down a little bit, but that's why last year he was so frustrated that he wasn't able to contribute more to our team. He just needed some time away from the game to get healed up. So hopefully we catch lightning in a bottle so to speak and Percy is back to himself."
Harvin arrives just in time to face his old team on Monday, the Seattle Seahawks, but it's unlikely the pass-catcher will be much help this week after not taking a snap in 13 months.
It's fair to wonder what Harvin has left in the tank, but -- when healthy -- he's proven to be one of football's most exciting players since entering the league in 2009. Notched at 4-4 and fighting for a playoff spot, Buffalo could use a spark.