At the end of an unusually full season, Serena Williams has described her fuel tank as empty. The world No.1 struggled into the final of the WTA Championships with an emotional, dramatic and rather strange three-set defeat of seventh seed Jelena Jankovic. New world No.3 Li Na awaits.
Never before has Williams played over 80 times in a season, and her serve and movement appeared compromised for much of her 6-4, 2-6, 6-4 elimination of Jankovic in match No.81, win No.77. The 32-year-old looked listless, forlorn, distressed at times during a contest she had been expected to dominate as she had the three round-robin contests before it.
Williams said she had "hit a wall" of fatigue when lying down in her hotel room the previous night; Jankovic said it was difficult to play against someone who "for some reason, every time she starts losing, she starts serving slower or not running for certain balls", and, rather pointedly mentioning that good sportsmanship was important, whatever the circumstances.
"Physically I was so tired just even standing," said Williams, unsure how she had pulled herself through, and needing four match points and two attempts to serve it out. "My legs wouldn't move. My arm wouldn't go fast. I think when you are doing something so much for so long throughout the year, maybe it can take its toll. At the end of the match, I was really just fighting just to stay in there and just try and get my legs to move to go to the balls."
And Sunday? How much is left? "Right now I'm on 'E' (empty). We'll see," she said. "I'm going to obviously try to put some gas in the tank tonight, go to the gas station and fill up and try. We'll see what I can do. Like I said, I'm really proud that I was even able to stay out there today.
"And tomorrow is the final, so obviously everyone gets pumped up. I'm hoping I'll get some adrenalin going tomorrow. I need to lay down for 24 hours and that's it, I think. But I don't have that time, so I'll try."
Li, she said, was a threatening opponent, as well as - at 31 - a mature contemporary. The 2011 French Open champion had set herself a top-three goal at the start of 2013, as a personal best and to break her tie with Japan's Kimiko Date-Krumm as the highest-ranked Asian player ever. A second grand slam title was the other half a mission that was partially accomplished in a season that now has just one match left to go.
"Now I catch the top three. Tomorrow is the last match. So enjoy and (then) have a good vacation. This is my goal," said Li, who has now overtaken Maria Sharapova and Agnieszka Radwanska to trail only Williams and second-ranked Victoria Azarenka. "I like to be first, you know," she quipped about being the all-time Asian No.1. So is world No.2 her next ambition? "Why not?" she smiled.
But, first, the final, and the enormous obstacle that is Williams, her fatigue issues notwithstanding. The American leads 9-1 in career meetings, most recently a 6-0, 6-3 belting at this year's US Open, in which Li admitted she was beaten before she started.
No other player is capable of such intimidation but, then, there is only one Serena. "I don't think another player give me the same feeling," said Li. "Actually, when I was walking to the court, I was still feeling confident, but after one or two games, I couldn't find the rhythm during the match against Serena in the US Open." Asked what will be different this time, Li joked that she would not "look at her at all". The ostrich approach. Worth a try. Anything is.
Kvitova, who in recent months has salvaged a good amount from a not-great year, tipped Williams. "It's always a chance here, for sure, but I think Serena is favourite," she said. "Li Na played really good this tournament (but) I think if I be honest (I'd) say like 70 per cent for Serena."
Jankovic, too, can take much from an improved season she ended a little sceptical about Williams' explanation of fatigue for a semi-final of such fits and starts.
"I have a cold, and maybe if I start losing I start dragging myself and not run for balls, I can do the same. It's how you want to play the game. That's up to you. And there is nothing wrong with that. We are all competitors and you compete the way you want to compete," said Jankovic, noting that Williams had a rest day on Friday after three straight-sets matches, but also relating to the toll taken by 80-plus matches for the year.
Williams has played 15 only tournaments, but extra activity has come through winning 10 - perhaps 11 - of them. "I think my problem more or less is I have played so much this year, more than I have in my whole career, which is ironic, because obviously I'm older than I have been in my whole career," laughed the 17-time major champion. "Seeing me playing so much more than everyone else is shocking. I don't really play that much tennis."