The Centurion Captive (The Champions, #3.5)

Once a Centurion rising through the ranks of the Legion of the Republic Julius had his eyes set on the future and glory. There was a time when Julius Lucius, the bodyguard of Velletri's champion, saw slaves, even gladiators as property to be made use of. He never dreamed that one day he would become one.

It was a tactical error on a simple mission that changed everything in his world. One morning he was a soldier and the next he woke as a prisoner that would be forced into slavery to survive...