Let the Hall of Fame debates officially begin ... Jamaal Charles is calling it an NFL career -- reportedly set to sign a 1-day deal with the Chiefs to retire this week.
The legendary RB told TMZ Sports earlier this month his football future was "up in the air" ... but 610 Sports Radio reported Tuesday he'll ink a ceremonial deal and officially hang up his cleats shortly.
It's not too surprising ... Charles hadn't started a single game since the 2015 season -- and told us earlier this month it was "a possibility" this day could come.