Gennady Golovkin branded Adalaide Byrd's disputed scorecard as "very bad for boxing" after his draw with Saul 'Canelo' Alvarez in Las Vegas.
Byrd gave Alvarez 10 of the 12 rounds in Las Vegas, scoring the world middleweight contest 118-110 in favour of the challenger.
A largely pro-Mexican crowd immediately made its displeasure known, and even Alvarez's promoter Oscar De La Hoya called the judge's interpretation "a shocker".
Golovkin was given a 115-113 verdict while the third judge scored it 114-114, leaving both fighters to claim moral victory and call for a rematch.
"I saw computer, all total punches, I saw people's reaction," said Golovkin, who landed 218 punches to his opponent's 169. "It's terrible, for me it's terrible. This is not correct, this is very bad for the sport."
Boxing dignitaries weighed in on social media, Lennox Lewis among those to criticise the scoring, while GGG mocked his rival for failing to fight like a true Mexican.
"He talked too much before the fight," the Kazakh said. "He said he's a true Mexican man [and that he would] bring Mexican style. But he moved every round, moving, not staying."
An unrepentant Alvarez said: "I wasn't taking points round-by-round but what I am sure of at the end of the fight was that I won. I have no doubt in my mind, I won the fight."
De La Hoya, unsurprisingly, agreed - even if he did not shirk when it came to criticising Byrd.
"These guys fought their heart out," he said. "Gennady is a tremendous, tremendous champion and Canelo's a tremendous, tremendous champion. Everybody has their opinion but that's what made it such a great, great fight.
"The 118-110, I don't understand, I really don't. Byrd is a very competent judge but I just don't understand 118-110. I had Canelo winning seven-five. 118-110 is a shocker."