NEW YORK (AFP) - Former world number one Caroline Wozniacki booked a return to the US Open final on Friday as China's Peng Shuai was stricken by heat-related illness and retired from their semi-final in tears.
Peng was taken from the court in a wheelchair as Wozniacki, leading 7-6 (7/1), 4-3, was declared the victor.
Peng, in growing discomfort in the second set in the hot sunshine bathing Arthur Ashe Stadium court, was overcome in the eighth game, reeling to the back of the court where she was eventually attended by a trainer and a supervisor.
After some discussion she was helped form the court and granted a confusing and controversial mid-game medical timeout as Wozniacki was left to try to stay loose hitting practice serves.
Peng returned to the court and after a break of 10 minutes played five more points before she was stricken again, finally crumpling to the court, her Grand Slam dream in tatters.
"She was in distress, she had a heat-related illness," said tournament director David Brewer after the match, adding that Peng was recovering well in the on-site medical facility.
Wozniacki joined the officials at her side and soon thereafter the umpire pronounced the final score.
"It was very difficult to watch," said Wozniacki, who offered Peng a comforting pat. "Tennis is great but the health is more important. I wanted to make sure that she's OK." Wozniacki was especially concerned knowing that Peng had surgery to correct a heart defect as a youngster.
She wasn't too concerned about whether the extended break broke any rule.
"I didn't really know the rules - I know if it's just cramping you aren't allowed to have a timeout but if it's heat illness you can," she said.
Wozniacki, who shocked five-time Grand Slam champion Maria Sharapova in the fourth round, is back in a Grand Slam final for the first time since losing in the 2009 US Open final to Kim Clijsters.
The 10th-seeded Dane will play for the title on Sunday against either two-time defending champion Serena Williams or first-time Grand Slam semi-finalist Ekaterina Makarova of Russia.
"It's incredible to be in the final, I have goosebumps," said Wozniacki, a 22-time WTA Tour winner who hadn't reached a major semi-final since the 2011 US Open, when she was ousted by Williams. "I'll go to have an ice bath, then watch the other semi." - Uncomfortable viewing -
Peng's agony made for uncomfortable viewing.
"I feel sick to my stomach just watching this," said tennis legend John McEnroe, commentating for US broadcaster CBS.
Peng, 28, had made it out of the fourth round at a Grand Slam in her 37th attempt and was trying to join double major winner Li Na as the only Chinese players to reach a final of one of the game's most elite events.
Unseeded and ranked 39th in the world, she knocked out three seeds on her way to the semi-finals, including number four Agnieszka Radwanska.
Matching Wozniacki in a punishing battle of baseline rallies - some of them reaching 20 shots or more - Peng made particularly good use of her two-handed backhand in the early going, and gained the first break for a 4-3 lead in the opening set.
Although Wozniacki immediately broke back, Peng broke again for 6-5 lead and a chance to serve for the set, but the Dane again recovered the break to force a tiebreaker which Peng surrendered quickly with three groundstroke errors on the final points.
Peng again seized the initiative in the second set, breaking Wozniacki in the second game only to surrender her serve in the next.
She gifted Wozniacki a triple break chance with a double fault in the fifth game, and Wozniacki seized the opportunity with a sizzling service return off a cautious second serve.
By then, Peng was already struggling, bending over between points and grimacing in a preview of what was to come.