PARIS — At changeovers in her French Open semifinal, an ill Serena Williams walked ever so slowly to the sideline, where even lowering herself to sit down seemed difficult.
With the temperature nearing 85 degrees (30 Celsius) on the hottest day of the tournament, she pressed white towels filled with ice against her forehead and neck and guzzled water.
In the early going, her play was as poor as her health. She failed to chase balls she normally would. As telling as anything: Even when she won points, Williams mostly refrained from her familiar fist pumps and yells of "Come on!"
Never can count her out, though, no matter the circumstances. Down a set and a break Thursday, and clearly not herself, Williams summoned the resolve to reach the final by beating 23rd-seeded Timea Bacsinszky of Switzerland 4-6, 6-3, 6-0.
After getting broken to fall behind 3-2 in the second set, Williams claimed the final 10 games.
"Stunning," said Williams' coach, Patrick Mouratoglou. "This is the difference between champions and everyone else. There is no logical explanation. She just has an ability to react when she is in danger."
Mouratoglou said the No. 1-ranked Williams has been dealing for several days with the flu, including a fever and chest congestion that "makes it difficult to breathe."
Now one victory from her third French Open championship and 20th major title overall, Williams faces 13th-seeded Lucie Safarova of the Czech Republic in Saturday's final.
"I tried everything. I thought if I lose, I will lose with a fight," Williams told the Court Philippe Chatrier crowd in French. "I tried, I tried. I found the energy. I don't know where, but I found it. And I won. I hope that on Saturday, I hope ..."
Cutting herself off, she stepped away from the microphone, bent over and began coughing. She offered a quick wave, then collected her things and left. Off the court, she got a hug from Mouratoglou, who helped her down stairs toward the locker room.
"I was worried," Williams' mother, Oracene Price, told The Associated Press. "But I knew if she could get through the second set, somehow maybe the adrenaline and God would help her get through the match."
Next comes Williams' 24th Grand Slam final, and Safarova's first.
The left-handed Safarova eliminated defending champion Maria Sharapova in the fourth round, then defeated 2008 French Open winner Ana Ivanovic 7-5, 7-5 on Thursday.
Williams won her semifinal despite dropping the first set for the fourth time in six matches. She'd never fashioned that many comebacks at a single Grand Slam tournament over her long, successful career.
When this one was over, finally over, Williams leaned forward and rested her head on her hands atop the handle of her upside-down racket. After greeting Williams at the net, Bacsinszky wiped tears from her eyes as she left, her magical run over abruptly. Before these two weeks, Bacsinszky never had been past the second round in Paris — or past the third round at any major.
Two years ago, she took a hiatus from tennis to work at restaurants with an eye toward pursuing a degree in hotel management. Last year, she was ranked 112th and went through qualifying simply to get into the French Open's main draw.
This year, equipped with a dangerous backhand and an affinity for delicate drop shots, Bacsinszky beat two-time Wimbledon champion Petra Kvitova, who was seeded fourth, along with No. 16 Madison Keys of the U.S., and lost a tournament-low 33 games entering Thursday. She also was 7-0 for her career at the French Open when winning the first set.
Ah, but none of those matches came against Williams.
When the chips are down and the going gets toughest, no one is better than her at the moment — and, perhaps, in the history of the game. She is 11-0 in three-set matches this season, part of an overall record of 31-1.
If she can get past Safarova, the 33-year-old Williams would add to her French Open titles from 2002 and 2013 and collect a third consecutive major championship, following those at the U.S. Open last September and Australian Open this January.
"She has been sick for a while, but she never thought about withdrawing," Mouratoglou said. "Even on one leg, she will step on court. She always believes that she can pull through. This is her strength. You can't take it away from her."
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