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When fighters announce their retirement, this usually entails a loss of desire to continue. This is especially true for boxers who have been at the top of their division for as many years as Klitschko has.
Klitschko has announced that he is thinking of retirement following a strong 2012 campaign that includes Chisora.
Sugar Ray Leonard (36-3-1, 25 KO) is an infamous example of a man whose years of constant playing with retirement cost him dearly. Before any talk of retirement, Leonard's record was 32-1. He retired, returned and repeated the cycle until he was finally beaten into retirement. Leonard's post-retirement comeback record was 4-2-1.
Klitschko already retired once in 2004, with an announcement made in 2005. Since returning in 2008, Klitschko has gone undefeated. The difference is that Klitschko has faced a far weaker field than Leonard.
One thing Leonard had over Klitschko in this situation was that he was still living out his mid-to-late 30s during post-retirement. Klitschko is 40 years old already.
Chisora's speed, youth and vitality can take Klitschko by surprise. Klitschko hasn't fought a fighter under 30 since Chris Arreola (34-2, 29 KO). Youth can be the big difference.
Leonard was obliterated at 34 by a 23-year-old Terry Norris (47-9, 31 KO) in 1991.
Klitschko is skilled, big and strong, but will he be successful on Feb. 18 when he defends his title against Chisora? The answer will be found this Saturday at 4:30 PM ET on Epix and EpixHD.com.