Athletic prowess is a double-edged sword: part gift and part gumption, some luck blended with sacrifice, pain and, on a few occasions, true glory. Olympic races produce such moments, and swimmer Michael Phelps now has experienced more of them than any other athlete, including a part in the stunning 4 × 100-m-relay win anchored by Jason Lezak.
If Phelps seemed nonchalant about the honor of Greatest Olympian--"It's a pretty cool title, I guess," he said--it's not because he doesn't appreciate or respect what it means. He has always been ambivalent about his achievements, yearning for the thrill of racing but struck...