The Wigan striker, who was celebrating both his wife's pregnancy and scoring a winning goal hours earlier, was repeatedly "cold-shouldered" by women revellers in London's packed Soho Revue Bar last December.
When a slightly-built university student became the latest to recoil from his touch, he lost his temper and in an outburst of "completely gratuitous violence" lashed out, "smashing" her to the floor.
His single clenched fist blow was so powerful that two other revellers - one of them holding on to his arm - were also sent flying.
While bouncers moved in to restrain the muscular £5 million striker, friends rushed to the aid of his victim.
As she was helped to her feet, blood poured from her shattered nose, London's Southwark Crown Court heard.
The 29-year-old, from Waltham Cross, Hertfordshire, claimed he was a victim of "mistaken identity".
But after hearing overwhelming evidence from a string of witnesses, including a football coach who insisted he was the assailant, the jury decided he was lying.
He was unanimously convicted of sexually assaulting the 20-year-old and causing actual bodily harm.