Kubrat Pulev suffered from a "pneumonia stage of COVID-19" while training for his December heavyweight title challenge of Anthony Joshua, something his co-promoter Ivaylo Gotzev claims hindered his chances of winning on the night.
Pulev was dragged into deep waters several times during his Dec. 12 defeat to Joshua at the SSE Arena, Wembley, before being finished off in Round 9. It was only his second professional defeat, with both coming in his two attempts to become world champion following a similar loss to Wladimir Klitschko in 2014.
Gotzev says Pulev is determined to try and earn a second chance at Joshua, adding that cancelling the fight was not an option after the Bulgarian had to give up the opportunity in the past.
"He didn't really have the power or the strength, nor did he have the sparring that he needed in preparation," Gotzev told Sky Sports. "Once again, not excuses, just facts, and that's what happened."
A serious shoulder injury forced Pulev to pull out of his first planned challenge of a then-undefeated Joshua back in October 2017, and the 39-year-old did not feel he could afford to postpone a second time, continued Gotzev.
"He says, 'No, I'm going through with it, I'm going to fight AJ, and I know I might never get a third chance at this fight ever again,'" the promoter explained.
"It was too much to lose, not fighting for all those belts. He really believed in himself. He had a shot at cracking through AJ and he tried.
"Within a month prior to the fight, he had Covid. He had to alter his training and quite honestly I thought we were going home. Me to the US, him to Bulgaria. He met with doctors and he made a decision. He is standing by his decision. He's a warrior.
"Look, we've always given AJ credit, and I'm giving him credit now, saying he's a great athletic specimen. He's fit, he's physically strong, he can punch, but the weaknesses are obvious. There were glimpses of that when AJ was getting frustrated every time that Kubrat got close and punched him. Kubrat just didn't have enough.
"It does take your strength. Kubrat, his X-rays showed he went through a pneumonia stage, but he fought it off and he was there for the fight."
With 'AJ' winning the fight decisively nonetheless, it's likely the champ will now move on to a potential megafight to crown an undisputed champion against WBC titleholder Tyson Fury.
And if Pulev must win a big fight elsewhere to bounce back into contention, Gotzev believes a good target could be Dillian Whyte, whose attempt to avenge his August loss to Alexander Povetkin has endured continued delays due to the Russian struggling with COVID-19 himself.
"Let's not forget that right now we stand still in a winning column with Kubrat at 2-1 against top British heavyweights," said Gotzev. "I'm referring to Dereck Chisora and Hughie Fury, so let's keep the score going.
"Certainly one fight of great interest that I think style-wise and personalities would make for a great clash is Kubrat Pulev versus Dillian Whyte, once he deals with Povetkin.
"Dillian Whyte has been very loud in the past talking about Kubrat and Kubrat feels like he is the perfect mouth he wants to shut. That's a great heavyweight scrap for the future."