The finest athletes of ancient Greece were already trained in hand-to-hand combat.

There are indications that Greek athletes, particularly pankratiasts and boxers, participated as gladiators in Roman arenas, either for money, or because they were captured or forced into it.

When Rome conquered Greece, the Romans were amazed by the Greeks’ martial arts, especially pankration (a brutal form of wrestling-boxing). Some former Olympic champions or Panhellenic athletes were recruited or persuaded to become gladiators due to their fame and strength.

The Roman writer Juvenal mentions that "Greek athletes, who gained glory at Olympia, ended up fighting as gladiators for the entertainment of the Romans."

Pankration was so violent that it was often compared to gladiatorial combat. The Romans adopted this martial art and trained gladiators in similar techniques.

Some pankratiasts and boxers were either captured and forced to fight, or persuaded by the Romans to join the arenas as professional gladiators, offered money and fame.

The best athletes of ancient Greece were already trained in hand-to-hand combat, which made them ideal candidates for the gladiatorial games.

Callias of Rhodes is cited as one of the toughest pankratiasts, who likely participated in Roman arenas.

Cleitus of Rhodes is rumored to have been called to compete in a Roman arena after his victories in Greek competitions.

Reports suggest that Roman gladiators were trained by Greek pankratiasts because of their expertise in unarmed combat.