AGGRESSION is n't new in football .
Mild - mannered Bayern Munich manager Pep Guardiola showed he too could mix it with the game 's tough guys after going toe to toe with AC Milan midfielder Nigel de Jong .
AGGRESSION is n't new in football but mild - mannered Bayern Munich manager Pep Guardiola showed he too could mix it with the game 's tough guys after going toe to toe with AC Milan midfielder Nigel de Jong .