5. Bjorn Borg

Sport: Tennis
Retirement Age (Career): 26 (1973-1983)
To this day many argue that if Bjorn Borg had kept playing, he would easily be the greatest to ever pick up a racquet. At the young age of 26 and on the heels of five straight Wimbledon titles, Borg hung it up. He left the game with 11 Grand Slams under his belt, the consecutive wins streak (43) and the only player to win the French Open and Wimbledon in three straight years. His endurance and cool under pressure set him apart from his peers. Sadly, eight years later, Borg returned to the game as a shell of his former self and failed to win a single match over two years before hanging it up for good. #smh #c'monson #toooldforthatshit