Nicolas Jover's gesture to shake hands with Kyle Walker enraged the Manchester City defender at the end of Sunday's 1-0 defeat at Arsenal.
The pair had to be separated after the final whistle as Walker first blanked the Arsenal coach's offer to shake hands before squaring up to him after something was said.
Former City set-piece coach Jover had refused to shake the hands of his former colleagues home and away last season as the Sky Blues won both games. But on Sunday he changed his approach and this set off Walker.
The Sun says he admitted this was the reason for his anger to teammates in the away dressing room after the melee.
Meanwhile, the FA have confirmed they will not be taking any action against Walker or Jover over the incident.