Colwill, who is just 21 years old, reacted angrily to a late challenge by the Irishman, grabbing his shirt by the collar before leading the game to be stopped before it could even start.
Their scrap was the main talking point after the game as Chelsea had to rely on a 82nd-minute equaliser from Lesley Ugochukwu to avoid what would have been an embarrassing loss to League One side Wrexham.
McClean’s early challenge on Colwill was mistimed but the English defender instantly latched onto the Irishman as the pair started wrestling each other.
Players and coaches from both teams had to pry the pair apart however both of them left the incident without punishment from the referee most likely due to it being so early in the game.
Next Chelsea will face Celtic, Club America, Manchester City, and Real Madrid across the next 11 days.