Oscar Valdez and Robson Conceicao are both undefeated boxers with a rivalry that dates back to their time as amateur fighters. Yet, it’s a series of decisions outside the ring that are overshadowing any talk about their Friday night fight at Casino Del Sol in Tucson, Arizona.

Valdez Conceicao odds
Oscar Valdez (left) will defend his WBC super featherweight title against Robson Conceicao (right) in a rematch of a 2009 amateur championship fight. (Image: Mike Williams/Top Rank/Getty)

Valdez tested positive for the banned substance phentermine last month, yet the Pascua Yaqui Tribe Athletic Commission ruled that the fight could still go forward.

WBC: No advantage from phentermine

The World Boxing Council also continued to sanction the bout. Valdez (29-0, 23 KOs) is the WBC super featherweight champion.

“It is simple, this is not a performance-enhancing drug,” WBC president Mauricio Sulaiman told ESPN last week. “If you go to a 7-Eleven and you steal a candy bar, you stole, it’s illegal, but that is different from robbing a bank with guns and pistols that will give you seven years in jail. Valdez will have absolutely no advantage and the challenger will have no risk.”

The World Anti-Doping Association (WADA) rules don’t ban phentermine outside of competition, only during the in-competition period. Valdez tested positive for the stimulant on Aug. 13, but was negative for phentermine on Aug. 30.

But the WBC uses the Voluntary Anti-Doping Association (VADA), and Valdez enrolled himself in the program, which is how the phentermine test came to light. VADA does not prescribe punishments for fighters, though the WBC, other organizing bodies, and regulators have issued punishments based on VADA findings.

Valdez maintains he has no knowledge of how phentermine entered his body.

“What I can say is that I’m a 100% clean fighter,” Valdez told ESPN’s Mark Kriegel. “I know every fighter is responsible for whatever they consume, but on behalf of myself, I have no clear answer on how that got into my body.”

Valdez, Conceicao clashed in amateur ranks

In any case, the fight will go on this Friday. In a way, this is a rematch of sorts, and Conceicao (16-0, 8 KOs) won their first bout. That battle came in the 2009 Pan American Games, with Conceicao emerging victorious by a single point in the gold medal match. The Brazilian would go on to win a gold medal at the 2016 Summer Olympics.

“When I fought him, it was a tough fight,” Conceicao told reporters. “I fought him and the crowd, and it motivated me a lot and made me happy. Here we have the same thing. I fight against two opponents, him and the crowd … and I will be the winner.”

Valdez says he wants revenge for that loss, and he appears very likely to get it. While Valdez comes into the fight as the consensus top super featherweight in the world, Conceicao doesn’t appear anywhere on any major lists. BoxRec ranks the Brazilian as 46th in the division, as he hasn’t fought any top-level competition – and certainly nobody on the level of Valdez.

As such, Valdez enters as a -2000 favorite according to PointsBet, and the champion says he doesn’t plan to lose to Conceicao (+850) again.

“Everybody hates losing, and I’m one of them. I’m a sore loser,” Valdez told reporters. “I’m defending my title, and I’m going to do whatever it takes and whatever I got to defend my title and avenge my loss.”