Rybakina's withdrawal just 10 days before the start of the US Open raised concerns over the fitness of the world number two Kazakh, who lost in the final of last week's Toronto event to Swiatek.
Trailing 4-1 in the opening set of Thursday's Cincinnati quarter-final, Rybakina suddenly pulled up short at 40-all, heading to her bench and consulting with the trainer.
She went back out and played one more point before quitting.
"I was feeling anxious watching the whole situation," said her opponent Swiatek. "I hope she will be fine. Health is always the priority."
"This is an important tournament, but the US Open is the US Open. I hope she is ready for that," she said, referring to the major which begins in New York on August 30.
"It was a shame she was injured, we were having a good match."
Had two-time Grand Slam winner Rybakina reached the Cincinnati final she would have risen to number one in the world for the first time in her career, following incumbent Aryna Sabalenka's shock exit to 20-year-old Sara Bejlek.
"I feel great, ready to play my game," added defending Cincinnati champion Swiatek.
"I've gained a lot of confidence in the last weeks. I'm happy to be playing the tennis that I am."
'Good record'
Poland's Swiatek now plays a semi-final against Jessica Pegula, who is reportedly carrying a hip niggle after defeating Amanda Anisimova 6-2, 4-6, 7-6 (7/4).
Sixth-seeded Anisimova converted all five of her break points against Pegula, breaking her three times in the second set, before the American rebounded to win.
Pegula is setting WTA records at age 32. She is the fourth player since 2009 to reach five or more Masters 1000 quarter-finals after turning 30, along with Li Na, Serena Williams and Svetlana Kuznetsova.
Pegula took charge early against Anisimova, needing just 34 minutes to pocket the opening set on the first of three chances.
But Anisimova struck back in the second, earning a double break for 4-0.
After Anisimova squared the match at one-set each, Pegula regrouped with an opening break in the deciding set.
They would each be broken twice as they went to the tiebreaker, where Pegula sealed the win on her first match point.
Pegula's win was her sixth without a loss to Anisimova.
"I know I have a good record against her, but literally every single match is like it was today," she said.
Sweet victory
In the men's draw, Flavio Cobolli advanced to the final four with a 2-6, 6-3, 6-4 defeat of Tommy Paul, gobbling down a handful of sweets for an unorthodox boost midway through the match.
The Roland Garros runner-up asked for the treats to be brought to the court and seemingly took energy from the pause before dispatching Paul, who had himself eliminated top seed Alexander Zverev 24 hours earlier.
"A sweet with chocolate makes me happy," Cobolli said. "I've tried it in doubles so why not singles?"
Cobolli mounted the comeback after dropping the opening set against Paul, one of four US men in the last-eight stage.
With the match tied at a set apiece, the American needed an extraordinary effort to hold serve for 4-3 in the final set, battling through five deuces and saving four break points.
But Cobolli ignored the showing as he closed out victory.
"It was a difficult day," the winner said. "I'm proud of my effort, my game and my mental strength. It is all good practice for the US Open.
"My shape is 100 percent. I may play golf tomorrow on a day off to relax but I will be ready to fight again."
Cobolli is the 11th different Italian to reach a Masters semi-finals since the series began 36 years ago.
His unusual candy break was somewhat reminiscent of the espresso shots often downed in the heat of battle by his compatriot Luciano Darderi.
© 2026 AFP
