Serena Williams fought back to beat Timea Bacsinszky and reach the French Open final despite struggling with illness.
The top seed took 10 games in a row to win 4-6 6-3 6-0 and set up a final against Lucie Safarova on Saturday.
Williams, 33, has been unwell throughout the tournament and struggled as temperatures soared in Paris.
“I don’t think I’ve ever been this sick,” Williams told ESPN. “I didn’t expect to win that, I really didn’t.”
She added: “I got the flu after my third-round match and I’ve been really struggling ever since then. Hopefully this is the worst and I’ll get better from here.
“I thought, ‘If I’m going to lose, I’m going to go for winners.’
“The next thing I know it was a set all and I thought, ‘I really don’t feel like playing a third set.’ I was so tired. I just fought for every point and here I am.”
The American world number one, who pulled out of her post-match media commitments, is trying to win her third French Open and 20th Grand Slam singles title.
Earlier on Court Philippe Chatrier, 13th seed Safarova fought back to beat Serbia’s Ana Ivanovic and become the first Czech woman to reach a Roland Garros final in 34 years.
Williams claimed her fourth victory in this tournament from a set down, something she has never managed before at a Grand Slam.
She looked down and out for the first set and a half against Bacsinszky, with the Swiss 23rd seed showing no nerves on her major semi-final debut.
Williams, meanwhile, wrapped herself in ice towels at the changeovers, shuffled slowly between points and looked close to breaking down at times.
Bacsinszky, 25, cracked a backhand return winner to go 3-2 up and served out the set, before moving a break up in the second after converting her sixth break point.
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Williams had kept herself in the contest thanks to her mighty serve, but finally broke the Swiss for the first time to level at 3-3 and then smacked away a backhand drive-volley for a decisive 5-3 lead.
Bacsinszky had hit 16 winners in the first set but that dropped to eight as she came under pressure in the second, and there were just two in a one-sided decider.
With victory all but assured at 5-0, Williams hit a superb running forehand pass on her way to securing victory – and a 24th Grand Slam final place – in a little under two hours.
“Every tennis match is tough,” said Bacsinszky, who left the court in tears.
“I’m not really looking at how my opponent is doing on the other side of the court. I’m more focusing on my plans.
“She’s the only one who knows how she was feeling. I have no idea how fit she was or not. I knew on court it would be a difficult match. I never forgot that.
“She deserved to win today. It happens. It’s only a tennis match.”
BBC SPORT