The seemingly real "switch" of winners in sports games back and forth in a grudge match, particularly in Fifa or Madden.
It's possible to win when you should lose, but it's harder. Maddenitis usually happens when the two players are around even skill level.
Person 1 and Person 2 are playing a sports game on their home console.
Person 1 starts off with the "upper hand" and plays with ease. This would mean that Player 2 has maddenitis, and next match, Player 1 will have it.
"Wow, the only reason you picked that was because of Maddenitis."