Mike Tyson almost got into a second fight after stepping into the ring with Roy Jones Jr. -- because some wacko swung on him trying to prove something ... TMZ Sports has learned.
Sources familiar with the situation tell us ... Mike was leaving Staples Center Saturday night after his bout with Roy -- which was called as a draw -- and on the way out, he came across a small group of fans looking for autographs.
When he walked over to do some signing, we're told a man in the crowd yelled out to Mike .