You don't expect a 25-year-old man to walk away from the game of football, but that's exactly what Ryan Winterswyk has done.
Why, I don't know, and I think it's better not to speculate until we hear more. Winterswyk was signed back in July as an undrafted free agent from Boise State, and his quality blocking chops made him an intriguing long-term project as the Falcons' third tight end. He spent 2011 on the team's practice squad and seemed likely to at least remain there this season.
I had Winterswyk making the team as the third, blocking tight end this season. Chances are good that the Falcons will now—if they weren't going to before—turn to a free agent or fellow practice squadder Tommy Gallarda. The Falcons are now critically low on tight end options, which means some kind of signing is very likely.
He could always come back, I suppose, but it sounds like he's hanging it up. Wherever he's going next, I wish him luck.