Dmitry Bivol will have a tough test on his hands if he wants to remain a champion.
Bivol must face top contender Gilberto "Zurdo" Ramirez in a mandatory defense, the World Boxing Association announced Wednesday. Ramirez is the No. 1 contender in the WBA's 175-pound ranking.
Bivol had requested to face London's Joshua Buatsi, per the WBA.
"After an extensive study of the same, the WBA denied such permission," the sanctioning body said in a tweet on Wednesday.
Bivol (20-0, 11 KOs) is coming off a landmark win against Canelo Alvarez, ESPN's top pound-for-pound fighter at the time. The Russian boxer won in a unanimous decision -- 115-113 on all three scorecards -- to successfully defend the belt for the eighth time.
Ramirez (44-0, 31 KOs) told ESPN he was surprised Bivol made the request to the WBA but was pleased with Wednesday's ruling.
"I felt that they were scared to fight me," Ramirez said. "That's why I'm so happy to fight him. I've been waiting for this moment for so long. Now it's my time."
The 31-year-old Mexican fighter is looking to become a two-division champion. In 2016, he made history by becoming the first Mexican to win a super middleweight title when he outpointed Arthur Abraham. It set the table for Alvarez, who ran through the 168-pound division to become the first undisputed super middleweight champion in the four-belt era.
The ruling also suggests that if the two sides cannot come to terms by the end of Wednesday, a purse bid will be held for the bout's rights. Matchroom Boxing promotes Bivol, and Golden Boy Promotions handles Ramirez.
If Bivol doesn't want to face Ramirez, he could vacate the WBA belt, since Badou Jack relinquished the title in 2017. However, Ramirez said he doesn't think Bivol will go that route. Ramirez said he feels he presents the most lucrative option for Bivol and believes there is an appetite to see if a Mexican fighter can dethrone Bivol, something Alvarez couldn't do in his ambitious attempt in May.
"It will be really surprising if he vacated the title," Ramirez told ESPN. "Who else is he going to fight?"
The matchup could be one of boxing's most competitive title bouts of the year. Bivol is No. 2 in ESPN's divisional rankings, trailing only Artur Beterbiev. Ramirez is slotted third following his win against Dominic Boesel in May.