Derek Fisher
Credit: Layne Murdoch / NBAE / Getty Images

Six months younger than Steve Nash, Derek Fisher is the NBA's second-oldest active player. The Oklahoma City Thunder point guard, in his 18th season, is a five-time NBA champion, but he played in only 33 games last year. How does an NBA player stay relevant and, more important, on the court? Some strength training is needed, Williams says, but "being able to exert yourself aerobically with high-energy" is more important. If Williams is right and the key is still being able to play defense and "really exert yourself in spurts," then Fisher may be in the final days of his career. He's been struggling with faster point guards, but he can still nail a three.