If successful, the 28-year-old challenger from KwaXimba, KwaZulu-Natal, will become the first African fighter in history to win the WBO strap in the cruiserweight class.
Corrie Sanders - a leftie just like Mchunu - was the first fromthe continent to win the same organisation's heavyweight belt after he flattened Ukrainian Wladimir Klitschko in two rounds in Germany in 2003.
"I will need to take him [Usyk] out of his comfort zone early - I must be quick and mobile.
"This fight will bring me back to the top, where I belong," said Mchunu, whose biggest championship fight to date will be televised on Home Box Office, America's biggest cable network.
Mchunu - who is under the guidance of trainer Sean Smith in Johannesburg - can win this bout but only if he gets out of his cocoon and fights to the bitter end.
He has the experience and big-fight mentality, having beaten prominent names, including former top heavyweight fighter Eddie "Fast" Chambers.
Mchunu's worst enemy is his impatience. He losses composure when things do not go his way.
Usyk, 29, still lacks experience in the professional ring.
The 2012 Olympic champion turned professional in 2013 and has 10 wins from as many bouts, with nine knockouts.
Meanwhile, topping the December 7 bill will be the legendary former multiple world champion Bernard Hopkins, 52.
The American will be involved in his last boxing match against Joe Smith Junior.