#4 Hershel Walker
Many of you might not know Hershel Walker, who is a retired American football player from USA. His professional football career lasted for 14 years from the year 1983 to 1997. The running back has been a two-time NFL Pro Bowl. The American came into the mixed martial arts field when it had been 12 years since he had retired from rugby. At the age of 47, Walker signed a contract with a MMA promotion company called Strikeforce. He would compete in their heavyweight division along with other athletes.
Therefore, in January 2010, Hershel fought his first fight in the MMA where he defeated Greg Nagy via technical knock-out strikes at Strikeforce: Miami. The CEO of Strikeforce, Scott Coker, announced that Walker would fight again next year against former WEC fighter Scott Carson. Walker beat Carson via technical knock-out in the first round and his MMA record stood at 2-0. But the former football player decided not to fight again with age not being on his side.