Denis Lebedev’s retirement ends up being a short one, as the former cruiserweight champion is set to return to action on December 21 against Thabiso Mchunu. Lebedev, who made his professional debut in 2001, won 21 straight fights before losing a WBO cruiserweight title fight to Marco Huck. Lebedev, however, went on to defeat James Toney for the interim WBA cruiserweight title in November…