The heavyweight fight between Francois Botha and Sonny Bill Williams could be in danger.
The All Blacks centre was taken to hospital for an MRI scan after hurting his shoulder in a rugby match for the Panasonic Wild Knights in Japan on Saturday.
Williams, who is also the New Zealand heavyweight champion, said on his Twitter page: "Going in for an MRI; hopefully just a small muscle tear.”
Panasonic won 23-20 win against Kintetsu Liners after Williams scored a first-minute try.
The talented midfielder had his right arm in a sling when he was taken to hospital after the match.
It was not immediately known if the injury was serious enough to put his fight against the South African at risk. They are scheduled to meet in Australia next month.
Botha, a former IBF heavyweight champion, said earlier this week Williams was in for a rude awakening.
"He's going to be hit harder than he's ever been hit. If I were in his shoes, I'd be shaking," said the 44-year-old Botha.
The fight was confirmed when World Sport Promotions announced in Durban it would take place in Brisbane on November 24.
The ten-round contest will be held in Australia because the organisers were unable to find sufficient financial backing for it to take place in South Africa.
Botha, nicknamed White Buffalo, knocked out Flo Simba last June. "I fought a 21-year-old who had ten knockouts and look what I did to him," he said. "I destroyed his career."
Williams, 27, has played in 19 internationals for New Zealand. He has won all five his professional fights. In his most recent bout, in February, he won the New Zealand title by knocking out Clarence Tillman in the first round.
"He's never been in this league, so let's see what he can do when he has a real fighter in front of him," Botha said on Tuesday.
"He is a superstar in rugby. He has worldwide acclaim. He's very popular now, being a boxer, so we're capturing fans of two sports. That's the only reason I'm doing this."
His coach, Hardy Mileham, insisted they were not underestimating the All Black star. “We've seen his boxing skills and he's not bad, but we're training thoroughly for ten rounds."
Williams said he was looking forward to the challenge. “I'll be stepping into the ring against a very experienced fighter who has all the great heavyweights of the past decade on his record," he said.
Botha, who once held the IBF title and has lost to some of the best heavyweights in the world, has a professional record of 48-8-3, including 29 knockouts.
His record also includes stoppage defeats against Mike Tyson, Lennox Lewis, Wladimir Klitschko, Evander Holyfield, Michael Grant and Michael Moorer.
Williams, rated as the best midfielder in international rugby, will probably by outweighed by 20 kg when he gets into the ring with the former SA amateur and professional champion.
Botha, who also held the World Boxing Foundation title at some stage, was in poor shape when he lost on points to Francesco Pieneta in Germany last month.
He briefly held the IBF title after beating Axel Schulz, a German, in 1995. The belt was taken away when he tested positive for an illegal substance.