Serena Williams overcame physical difficulties and emotional distress, as well as a stubborn opponent in Jelena Jankovic, before reaching the final of the WTA Championships with a 6-4, 2-6, 6-4 win.
The world No. 1 was due to tackle Li Na, the first Chinese player to reach the title match, after the former French Open champion defeated Petra Kvitova 6-4, 6-2.
It was a harrowing, stumbling performance by titleholder Williams over former world No. 1 Jankovic, for she appeared to have problems with her movement and twice sat weeping into her towel during change-overs.
She also committed 40 unforced errors amid her 40 winners and allowed a 5-1 final set lead to evaporate to within one point of 5-5, before finishing it with three trademark heavy blows.
“Last night, I was lying down and I hit a wall,” said Williams, presumably figuratively speaking. “And since then I have had no energy. In the match I was struggling for energy to play at all.”
It was evident immediately that all was not well with 32-year-old Williams on Saturday. She dropped her second service game and went 1-3 down, and although she recovered with some stunning ground strokes, she rarely served at full power, and often looked ponderous and labored.
It got worse in the second set as the errors flowed more frequently, which encouraged Jankovic to raise her level. The Serbian defended stoutly and was at times able to counterattack, breaking for 3-1 again, but this time extending it to 5-1 and 6-2.
During this phase Williams looked capable of drifting to defeat. She responded to her mistakes with gestures of dismay, slumped shoulders and despairing staggers, and seemed capable of compounding shot-making uncertainty with an unpredictable emotions.
Her mother, Oracene, sat with her head tilted on one side, while her coach Patrick Mouratoglou combined withdrawn expressions with sudden gestures of triumphal support.
In the end, when Williams’ four-game final-set lead all but disappeared, it was only the sheer power of her ball-striking ability and her desire to survive which prevailed, but it was a close-run thing.
She may need to raise her level to hang on to the title.
Li Na gave further evidence of a remarkable late-career surge during her performance against Kvitova, which followed very good wins over Victoria Azarenka and Jankovic.
Already the first Chinese singles player to win a Grand Slam, the 31-year-old Li is now assured of a highest-ever ranking of at least world No. 3 and her latest performances suggest she is still improving at an age when many players are deemed to be in decline.