World champion Wladimir Klitschko has admitted he has concerns whether challenger Alexander Povetkin will meet him in the ring on October 5 in Moscow after the Russian's two previous withdrawals.
Klitschko, 37, was first due to fight Povetkin in 2008, only for the Russian to injure his ankle while training, then the 33-year-old pulled out of a second bout two years later when his father died.
October's clash at Moscow's Olimpiyski Arena will settle which of the pair is the World Boxing Association's champion and the fight details were decided 10 days ago after Klitschko insisted that the drugs testing is done in Germany.
The Ukrainian, who faces his 24th world title fight, told Hamburg's Morgenpost he was "cautious in regards to Povetkin.
"In the past we twice agreed to fight and he withdrew. With Povetkin, you never know what happens," added Klitschko, whose WBO, IBF and IBO titles are also up for grabs in Moscow.
With Klitschko holding WBA "super" champion status since his 2011 win over Britain's David Haye and Povetkin deemed the governing body's regular belt holder, the bout has been ordered to decide which is the true champion.
Povetkin, the 2004 Olympic heavyweight champion, has an undefeated record with 18 knock-outs in 26 wins, but Klitschko, who won Olympic heavyweight gold at the 1996 Atlanta games, says he hopes the Russian does not cancel on him for a third time.
"He really listens to what other people say, I hope people tell him that he should fight," said Klitschko, who has 51 knock-outs in 60 wins with the last of his three defeats having come nearly a decade ago.
Both fighters will walk away with a small fortune from the fight, with Klitschko standing to make a career-high 13.13 million euros ($17.1 million, £11.3 million) from the fight and Povetkin 4.4 million.
The final date of the fight has only been set back following lengthy negotiations with the Klitschko camp refusing to have the Russians take care of the drugs testing, which will be conducted by Germany's National Anti-Doping Agency (NADA).
"I have a name to lose which is worth far more than the money I get from this fight," said Klitschko.
"I can't afford any inconsistencies."