Caroline Wozniacki, the most conspicuous addition to the world's top 10 this year, suffered a harrowing ordeal as she was left unattended in the middle of the court, twitching in agony with cramp, before playing through her ailments to reach the semi-finals of the WTA Championships.
The 19-year-old Dane was abandoned to a painful fate in the final game of her 6-0, 6-7, 6-4 defeat of Vera Zvonareva because she had already used her one permitted medical time out. Any further treatment would have cost her a match she had seemed likely to win for most of its courageously contested 168 minutes.
Amazingly, Wozniacki won 11 of the first 13 games, was denied one of her first two match points after a long drawn-out Hawkeye appeal from Zvonareva, and then slipped to 3-4 down in the final set before recovering, only to collapse with cramp twice in the final few rallies.
Once she pirouetted before falling, once she used her racket as a walking stick, and once, as she lay flat on her back, her whole body apparently caught up in spasms, it seemed that Wozniacki would never make it.
However she got up, and battled through four more agonising rallies to a 6-0, 6-7, 6-4 victory before limping off for treatment. She was unable to appear for a scheduled press conference. Few season-end tournament debuts have been as dramatic.
Wozniacki was given fluids, food and massage, and later said: "I just don't know how I will feel tomorrow. I will have to see how I am. But I intend to play."
Later Serena Williams followed her capture of the season-end world No1 ranking by reaching the semi-finals. She did that with 6-2, 6-4 win over Elena Dementieva, the Olympic champion, to whom she had lost three times this year. "I have never done well in the round robin format, and now I finally have," said Williams. "But now I'm so tired I'm gonna sleep all day tomorrow."