Shortly after, he signed up with Japanese promotion Pride Fighting Championship and was assigned to the Takada Dojo team, where he trained under Kazushi Sakuraba and other fighters in order to make the jump to the sport.

[3] Nastula did well during the match, holding his own in the grappling exchanges for the first half of the round, but his inexperience was evident when Nogueira capitalized on his striking superiority, getting the upper hand in the mat with several knees to the head.

After receiving a hard right hand, Nastula managed to get a takedown, but he was too tired to remain in the offensive role, and Nogueira found little resistance to unload ground and pound until the referee stop.

The judoka again showed an excellent performance, taking down Barnett several times and landing effective left hooks, but Josh reversed him later in the match and executed a toehold to submit Nastula.

Nastula has denied the veracity of the test results, however, claiming that the stimulants were absorbed into his system from over-the-counter supplements and that nandrolone, a mass-building substance, would not have been useful to him as he has not gained any muscle mass since coming to PRIDE.

Following the fall of PRIDE, Nastula signed with World Victory Road and competed at Sengoku 4, losing via a controversial TKO to Yang Dong Yi.

After Dong narrowly escaped an armbar attempt from the judoka, Nastula was unable to answer the referee's call to stand up, having received numerous strikes to the groin earlier in the fight.

At that moment, Nastula indicated problems with his protective cup, but instead of ordering it to be checked up, the referee inexplicably halted the bout and declared Yang the winner by TKO.

Nastula proved to be in shape, as he quickly knocked down his opponent and followed with a flurry of punches on the ground, forcing the referee to stop the bout early at 0:26 of the first round.