Just 1 day after signing with the Seattle Seahawks, tight end Luke Willson announced he's walking away from football for good ... reveling he was hospitalized with a severe heart condition earlier this year.
31-year-old Willson -- a 2013 5th round draft pick who won a Super Bowl with the Seahawks in 2014 -- resigned with his old squad on Tuesday.
But just a day later, the team said they were parting ways with Luke ... without explaining why.
On Wednesday, Willson provided some answers ... explaining he dealt with a serious heart issue a few months ago.