Spartacus was one of six gladiator recruits purchased by Batiatus. Of the six, five made it through training. Only three survived the final test, "the bridge of truth" (Varro, Spartacus, and Kerza).
Though it's not shown on screen, his presence in the following episode shows that Kerza managed to pass the final test with the use of only one eye; his right eye was still swollen shut from when Spartacus attacked him.
When Pietros is sent to retrieve a steel sword, the same type of "Thracian" sword that Spartacus' wielded in the previous episode can be seen inside the chest of weapons.