in the last few months, Williams is unofficial favourite to deny top-seeded Victoria Azarenka and second-seeded Maria Sharapova at the women's tour's season-end event.
The 31-year-old Williams has achieved all this despite the blood clots in her lungs which endangered her life and contributed to a 12-month absence during 2010 and 2011.
Nevertheless dissent has been articulated, notably at the influential magazine Sports Illustrated, at suggestions that the American legend should win the WTA Player of the Year award for a third time in five years.
Williams' commitment to the tour is being questioned again after she missed two of this year's four premier mandatory tournaments -- Indian Wells in March and Beijing last month.
Inevitably these absences have brought reminders of withdrawals which caused criticism in previous seasons.
As the WTA's four-year roadmap campaign places special emphasis on player commitment -- to avoid upsetting spectators and sponsors -- Williams' non-appearances may be regarded as relevant.
The roadmap has helped the tour's prize money to rise 51 percent, its player participation to improve 34 percent, and the achieving of record attendances and television coverage at some tournaments.
It may therefore also be a significant statistic that Azarenka, the world number one, the Australian Open champion, and the WTA Championships' top seed, has a superior record of matches played (75) and victories totalled (67) this year.
However, Williams, who has won 43 of her last 46 matches, struck a humble note after her startling recovery, claiming she now has "a whole new perspective on her life and career."
Certainly Williams has made a huge difference to the profile of women's tennis, but she does not have enough time left to climb back to become the year-end world number one.
Who gets that accolade will be decided over the next few days by Azarenka, who has been the ranking-topper for most of the year, and Sharapova, the former number one who achieved a career Grand Slam by winning the French Open in June.
Azarenka only needs to win two group matches to finish top, but if the Belarusian were unaccountably to win only one of these three round-robin encounters, Sharapova could snatch it away from her by taking the title.
Although the Russian celebrity remains the world's highest paid woman athlete, with an estimated annual income of $28 million, she has only won the WTA Championships once before, eight years ago during her breakthrough season aged 17.
Williams has won it twice, but the 23-year-old Azarenka's best so far is last year's runners-up position after losing a three-set final to Petra Kvitova.
Azarenka has also lost 10 of her 11 meetings with Williams, including at Wimbledon, the Olympics and the US Open this year, though she may take encouragement from having led 5-3 in the final set during the New York final.
In Sunday's draw, Azarenka gained an early chance to make up for her heartbreaker in the US Open final when Williams was drawn into her round-robin four, the Red Group, along with Li Na and Angelique Kerber.
This left Sharapova with a slightly less difficult looking quartet, even though the White Group includes Kvitova, as well as Agnieszka Radwanska and Sara Errani.
For the first time in the WTA Championships' 40-year history, the players come from eight different countries.
Kvitova, the former Wimbledon champion, is Czech, Radwanska, the Wimbledon runner-up, is Polish, and Li, the former French Open champion, is Chinese.
The two debutants, Kerber, a Wimbledon semi-finalist, and Errani, the French Open runner-up, are German and Italian respectively.