Seamus Lavelle - 6ft 3in tall and weighing 16 stone - died from a head injury within 48 hours of being felled by William Hardy, 25, during a game between Hendon and Centaurs rugby union clubs on 13 March last year, it was alleged.
David Spens, for the prosecution, said: 'Towards the end of the match Hardy deliberately punched Mr Lavelle on the jaw . . . it was an uppercut and impacted on the chin.'
The force of the blow caused Mr Lavelle, 30, to lose consciousness. His knees buckled and as he fell backwards his head struck the ground. He was put on a life-support machine in hospital, but died two days later. Mr Hardy, from Chiswick, west London, denies Mr Lavelle's manslaughter.
The trial continues today.