Only the new on fire player (after the update), spread the effect to other player. But it seems only spread to the nearest player/position. Cause i get 2 players on fire yesterday (DEF position in the squad), and i get 2 more players on fire in the same position (DEF). I played 4-3-1-2. Today, i get 1 reserve player on fire, but not getting more on fire. I think only in the squad team, don't know for the subs players.