British boxer, Umar Sadiq, was reportedly rushed to hospital following his defeat to Fyodor Chudinov.
The 32-year-old needed oxygen and started to “cough up blood” after the fight in Khimki, near Moscow.
Sadiq was disorientated after the WBA gold belt showdown.
According to Russian source TASS, he fell ill during routine doping checks.
An ambulance was called as the super middleweight began to “cough up blood”.
There has been no update on his condition since he arrived at the hospital in Russia.
Sadiq, who entered the bout with 10 wins under his belt, took the fight against Chudinov at short notice.
Speaking from his hotel room in Russia this week, he admitted preparations for the fight had been “very rushed”.
He told the Mirror: “If I wasn’t confident of winning I wouldn’t be out here because let’s face, I didn’t have to take the fight did I?
“As much as I’m the one getting in the ring, it’s still a team effort and I’ve got great people around me which is why I say ‘we’. Together, we’re here to do the business.
“It’s all been very rushed, sudden and out of nowhere but when you stay ready then you’re ready to grab opportunities like this by the horns and that’s what I’m doing.
“Chudinov, right now, as we speak is third in line with the WBA and with all the governing bodies he’s ranked in the top five or the top six.
“I know that I will literally be one of the top middleweights in the world after Friday night as long as I get the job so it’s a massive opportunity.”
Danny Williams, who beat Mike Tyson in 2004, fought on the same card.
The 47-year-old’s opponent, Sergei Kharitonov, walked to the ring with a BEAR before the fight.