In a cover story for last week's issue of Sports Illustrated, L. Jon Wertheim contended that Serena Williams was the greatest tennis player of all time. His reasoning: Though Serena can't boast the Grand Slam titles of Court, Graf, Evert and Navratilova, her athleticism and serve make her the best who's ever played.

It's a compelling argument and one that's tough to debate. If Serena at her peak played Chris Evert at her peak, it'd be advantage Serena. (Though this point almost always tilts in favor of the modern athlete, who tend to be bigger, stronger and fitter than their historic counterparts. All eight men in the 100-meter final at the Beijing Olympics beat the time Jesse Owens won gold with in 1936, but it doesn't mean they were all better sprinters.) But is the G.O.A.T. designation based on talent alone?

Serena could have been the greatest ever but that was something that never seemed to motivate her thus far in her career. She misses long stretches of the tennis calendar because of dubious injuries (witness her recent foot ailment which may keep her out until the U.S. Open), at times seems more interested in hawking things on the Home Shopping Network and isn't a dominant force in non-Grand Slams. Not that there's anything wrong with that.

Pursuing other interests and taking breaks from tennis could be part of the reason that Serena is able to dominate during the four events that matter. She knows that winning in Montreal doesn't mean nearly as much as winning in Flushing, so she sets her summer schedule to peak at the U.S. Open. The disinterest in July begets a passion for the game in September.

When she's on, Serena may be the best who ever played. Give me consistency and greatness though, like Martina winning 74 straight matches or Chrissie making the semifinals in her first 34 Grand Slams or Steffi winning the Golden Slam in '88. Greatness is about more than being dominant, it's about always striving to be that way.