I think we must not confuse "nasty" with "dirty". My definition of nasty is doing whatever it takes not to be cowed or intimidated by the opposition. If John Terry is putting his studs down your calves you give him some back. All the running and energy and never-say-die attitude is not going to make it stop but a forearm smash across face will.
He did today what he has been brought in for. He looks like he is lacking some match fitness which is understandable. He's going to help there is no doubt.