Chagaev is suffering from hepatitis B - the reason for the late cancellation of his WBA titlefight against Nikolai Valuev in Finland last month - and the American Association of Professional Ringside Physicians (AAPRP) is recommending the fight be postponed due to medical safety issues.
"Hepatitis B is a very virulent virus and easily transmitted," said the AAPRP in a statement. "It is even more important to be prudent in order to not only protect Mr. Chagaev's opponent, but also the referee, judges, sanctioning body officials, cornermen, ringside physicians and ringside observers who may be at risk of contracting this dangerous virus.
Calling boxing a "blood sport," the AAPRP said it was very common for blood to splatter on those ringside as well.
Klitschko, though, insists the fight must go on and claims he has the right innoculation to avoid contracting the virus.
"I am innoculated," said Klitschko, who holds the IBF and WBO titles while his brother Witali is the WBC champion. "Since I often travel in my role as an UNESCO Ambassador, I am often in the tropical institute getting injections."
The 33-year-old Wladimir had been scheduled to meet David Haye in in an open-air fight in front of 60,000 fight fans, but a back injury ruled out Haye and Chagaev has stepped in. As the only fighter to beat Valuev, Chagaev, the WBA's 'Champion in Recess' is also keen to prove his credentials.
Chagaev has spent more than a year out of the ring with an achilles tendon injury and his credibility needs a boost.
Victory on Saturday night would land him both of Klitschko's belts and make up for some of the disappointment of losing out on the Valuev fight and the chance to be undisputed WBA champion.
"I was furious and shocked when I heard the Valuev fight was off," said the undefeated Chagaev, 30, who has only fought twice since beating Valuev in April 2007 against Matt Skelton in January 2008 and Carl Davis Drumond last February.
Since he turned professional in 1997, Chagaev has 25 wins, one draw and 17 knock-outs to his record. But Klitschko - otherwise known as Dr Steelhammer - has an impressive 46 knock-outs from 52 fights and is eager to dispatch Chagaev to silence mutterings from the United States the division is dead.
"It's funny to hear the Americans say the heavyweight division is dead because in Europe the feeling is different," said Klitschko. "Forty-six opponents didn't make the distance out of 55 against me, so is that a boring record? I believe that my timing is getting better and in his
thirties a heavyweight fighter is getting stronger."