Is Serena Williams the greatest ever?

It is in the domain of the hypothetical to ask whether Serena Williams belongs in the conversation as the greatest female tennis player in history. But given the strong Serena vibe permeating this year's U.S. Open, why not?

Williams has been cast as an overwhelming choice to win the Open despite a year's absence from competition because of health issues; despite not having won at Flushing Meadows since 2008; despite the advanced tennis age of 30; despite being ranked 29th in the world.

"Not to undermine the rest of the field," said Chris Evert, herself a former member of the game's ruling elite, "but Serena is head and shoulders above the rest when she's healthy."

Williams' 13 career major singles titles pales in comparison with Margaret Court's record 24, Steffi Graf's 22, Helen Wills Moody's 19 and the 18 each by Evert and Martina Navratilova. Williams' total career tournament championships -- 39 -- isn't even on the radar compared with Navratilova (167), Evert (154) and Graf (107).

Although Graf once was ranked No. 1 for 186 consecutive weeks -- more than 3 1/2 years -- Navratilova for 156 weeks and Evert for 113, the longest Williams remained at the top of the rankings was 57 weeks.

Yet Evert said she would put Williams "right up there with Martina and Steffi. She's the best comeback player we've ever seen. Even when she hasn't been in shape, she can win a Grand Slam. She won the Australian Open when she was 20 pounds overweight.

"She's got the power, the speed, the mental toughness; there's no chink in her armor."

By acknowledging, for the first time this summer, her past failures to emphasize fitness -- and doing something about it -- Williams took things up a notch.

"There's nobody in history that I could put against her and say would win," said Cliff Drysdale, a tennis commentator who was a top pro in the 1960s and '70s. "In other words, I'm calling her the greatest of all time because she has no weakness. Not only no weakness, but so many strengths."

It is a sports cliche to traffic in such definitive statements, a fool's errand to compare eras, especially in what might be the sport most transformed over the decades because of revolutionary equipment and off-court training. (Baseball, for instance, has stuck with wooden bats. Not tennis.)

Would Graf at her peak have run Williams at her peak ragged, as tennis author Pete Bodo submitted? Or would Williams, with all else equal, be so athletically gifted that she could handle the pantheon of stars, going back to 1930s five-time major champion Alice Marble?

Marble, the first woman to serve-and-volley, "ended her career with a two-year winning streak," longtime tennis writer and broadcaster Bud Collins noted -- a feat that Williams, who regularly saves her best for Grand Slam events, hasn't approached.

Still, in the end, Collins would put Williams in the greatest-ever conversation -- "She's a marvelous competitor" -- along with Graf, Navratilova, Evert, "with [Monica] Seles in there somewhere," he said. "Billie Jean [King], too; she knew how to beat you."

It's all theoretical. Except for the women who will face Williams here.