By Serena Williams' standards, she has not been having a stellar season -- six titles in 14 tournaments, highlighted by a US Open win for her 18th Grand Slam title. It doesn't quite compare with 2013, when she had one of her best seasons, going 78-4 with 11 titles, including two Grand Slams.
Yet somehow, she seems to be further in front of the field than ever. That's because even if Williams has not been a model of consistency, her rivals -- to the extent she has any -- have been even more up and down. Other than Williams, Maria Sharapova has been the only player to win more than one of the bigger WTA tournaments, and there have been 32 different winners at the 45 WTA tournaments played this season.
The inconsistency has been even more visible at the majors, with four different winners playing four different finalists. The only player to even repeat as a semifinalist was Eugenie Bouchard, who reached two semifinals and a final in her breakthrough season.
These developments have reversed some of the order that was taking shape on the women's tour about a year ago. Back then, Williams was dominating the tour, but she also had Sharapova and Victoria Azarenka on her heels, creating a strong threesome at the top of the game.
Others, like Li Na and Agnieszka Radwanska, also were in the hunt, providing a sense of regularity that had been lacking for some time. But the others have slipped backward. Both Sharapova and Azarenka have been sidelined with injuries and still have not regained their form, while players like Li, Radwanska and Petra Kvitova have risen only to fall once again.
More positively, there are more players contending for the top positions. Former No. 1s like Ana Ivanovic, Caroline Wozniacki and Venus Williams have been showing glimpses of their former selves, while new names such as Simona Halep and Bouchard have become a firm presence in the top 10. This is also reflected further down in the rankings, where former Slam champions and finalists mingle among young talents.
With such a crowded field, the tour is competitive but also confounding -- it's hard to say what will happen next.
Another 18-time Grand Slam champion, Martina Navratilova, sees similarity of styles as the reason for the difference in performances.
"The players play one plan and they all play very similar styles, so it's just a matter who is better that day," she said at the US Open. "Nobody is repeating because of that. You just play a little bit better."
Former Grand Slam champion Tracy Austin agrees, citing "depth" and "inconsistency" as characteristics of the competition.
A prime example is Kvitova, who took the title at Wimbledon with a dominating performance in the final but did not win more than two matches at any of the other three majors and has been defeated in the opening round of five tournaments this year.
"I think Petra is a very talented player, very solid player," said Jana Novotna, another former Wimbledon champion and fellow Czech, who contrasted Kvitova's wins with her defeats. "And in my mind, as good as she is, she has no Plan B when Plan A is not working."
Though known for some wobbles herself, Novotna argued that players from her generation and previous ones did not have such swings. "We were more consistent," she said. "There was no way for someone, after winning Wimbledon, to lose two tournaments in the first round. Players maybe didn't play as much, but when they played, you were sure they were going to be in the quarterfinals, the semifinals at every tournament -- of not only the Grand Slams but every major tournament."
Without Serena, who has been playing more even as she keeps on winning, there would be even less semblance of order. But at age 32, she is likely to start having more uneven performances like this year.
Austin recalled that when Chris Evert retired at 34, the other 18-time Grand Slam champion's famed steadiness was not what it had been. "I remember her clearly saying that," said Austin. "There were more ebbs and flows."
"The average is maybe the same, but it's more difficult to play really good tennis," said Navratilova, who was 39 when she stopped playing singles regularly.
But with similar styles and similar ability, very good tennis is what it takes to win big titles these days, even for Williams. And until some solid opposition emerges behind her, it looks like the one consistency the WTA Tour can count on is inconsistency.