Serena Williams' "disappointment" with her 2013 season indicates her urgency to overtake the 18 grand slam titles of Martina Navratilova and Chris Evert and to get on with chasing Steffi Graf's Open era record of 22.
Whether the 32-year-old still has time to achieve that will become clearer at the season-ending climax, the WTA Championships which start on Tuesday.
It was an extraordinarily critical self-judgment by Williams on a season in which she has won another two grand slam titles (French and US Open) and taken her total to 17 - perhaps caused by a fear that time is short.
More than that, Williams has lost only four matches, taken her career earnings past $US50 million ($A51.85 million), and become the oldest woman to hold the world No.1 ranking.
She claims not to be mindful of such records, but volunteered that: "I'm excited about the possibilities".
Retaining the title this week will be a great momentum builder for her off-season work.
Williams is probably a stronger favourite this year, partly because of the absence of Maria Sharapova, who is rehabilitating her vulnerable shoulder.
The player most capable of upsetting her is Victoria Azarenka who has no doubt over where the American stands in tennis history.
"She can be the greatest of all time," Azarenka reckoned after losing to Williams last month in the longest US Open women's singles final in 30 years. "Serena's still not done."
The Belarusian also suggested the American focuses more intensely, and raises her level more dangerously when it really matters.
Williams has lost twice to Azarenka this year - in Doha in February the day after having regained the top ranking from her rival - and in Cincinnati in August after leading for most of the match.
Azarenka, at her best, has a chance of repeating these successes, because she has a big game and the boldness to try to impose it.
"Against her, you have to take risks because she will (do that), and she will do that really well."
But Azarenka will need to recover from a disappointing build-up to the WTA Championships. The world No.2 lost in the second round in Tokyo, where she had been feeling unwell, and in the first round in Beijing, where she served 15 double-faults.
The other six qualifiers in an eight-player field are Wimbledon finalist Agnieszka Radwanska of Poland, China's three-time grand slam finalist Li Na, Czech Petra Kvitova, Sara Errani of Italy, Serbia's former world No.1 Jelena Jankovic and Angelique Kerber of Germany.
Serena Williams (USA x1), Agnieszka Radwanska (POL x3), Petra Kvitova (CZE x5), Angelique Kerber (GER x8)
White Group:Victoria Azarenka (BLR x2), Li Na (CHN x4), Sara Errani (ITA x6), Jelena Jankovic (SRB x7)