Former Strikeforce title holder Nick Diaz challenged Georges St-Pierre for his UFC welterweight strap at UFC 158 this Saturday and he hasn’t been shy in letting the French-Canadian know he feels about him leading up to the fight.

While speaking to On The Fan 590, a Sportsnet radio station, the Cesar Gracie black belt in Brazilian Jiu-Jitsu accused the champion of using steroids and getting away with it (transcription via Bloody Elbow).

"I believe that he's is on plenty of steroids, and I don't think they test around here either. I doubt I'll be tested as well. I don't care what they say to the fans or the media, I don't think we'll be tested. And if so, he's probably got a bottle of piss in his pocket."

GSP denied using steroids at the pre-fight press conference earlier Thursday, but he was not present at the radio interview Diaz did.

Despite one of the best physiques in mixed martial arts, “Rush” has never had any controversy surrounding a drug test in 25 professional fights.

St-Pierre enters this long-awaited title fight on the strength of 10 consecutive wins, including a UFC record seven welterweight title defenses.

This is Diaz’s return fight after being suspended after UFC 143 for testing positive for marijuana metabolites. Diaz fought Carlos Condit for the interim UFC welterweight belt at the Feb. 2012 event, losing a close and controversial decision.

Prior to the loss, the Stockton, California native had won 11 straight contests inside the cage.

Will Diaz’s steady stream of trash talk be enough to get inside GSP’s head and throw him off his game or will this fight simply be business as usual for the dominant champion?