MIAMI GARDENS, Fla. -- Canada's Bianca Andreescu, the 2019 U.S. Open champion, left the court in a wheelchair due to a lower left leg injury in the second set of her Monday night match against 18th-seeded Ekaterina Alexandrova at the Miami Open.
There was no immediate word on the nature of the 22-year-old's injury or its severity.
Andreescu was trailing in the match at Hard Rock Stadium when, moving across the baseline, she fell to the court, clutching her lower left leg while screaming.
While staff was preparing the wheelchair to leave the court, Alexandrova, standing right at Andreescu's side, shared an emotional hug with her opponent. A short time later, Andreescu was wheeled off to a standing ovation.
Before staff arrived to aid her, the broadcast picked up Andreescu saying, "I've never felt this kind of pain before."
Andreescu had dropped the first set 7-6 (7) and was mounting a comeback, winning the first two games of the second set when she was forced to retire, allowing Alexandrova to advance.
Alexandrova will face Petra Kvitova in the quarterfinals. Earlier Monday, Kvitova defeated Varvara Gracheva 7-5, 7-6 (7).
Also, world No. 2 Aryna Sabalenka of Belarus defeated Barbora Krejcikova of the Czech Republic in straight sets in a match that started at 10:45 p.m. because of a two-hour rain delay. Sabalenka prevailed 6-3, 6-2 for her 20th win of the year and will face Sorana Cirstea in the quarterfinals Wednesday.
American Jessica Pegula, the No. 3 seed, dispatched Poland's Magda Linette 6-1, 7-5. Pegula advanced to face 27th-seeded Anastasia Potapova, a 6-4, 7-6 (7) winner over Qinwen Zheng, in Tuesday's quarterfinals.
The 29-year-old Pegula raced to a five-game lead in the opening set against Linette and then found herself tied at 5-all in the second set before closing out the win.
"I think after 5-2, I don't know what I was doing," she said. "It was, like ... The changeover before that I switched racquets because I thought maybe the ball was flying on me a little bit. It didn't feel very good. Switched back to the old racquet and I won the next five games.
"I don't know why that happened, but sometimes it does. I was mad at myself that I switched racquets in the first place because it was only one break. But we got through that little mental battle I had with myself, and I was able to play very well."
In a fourth-round matches, 10th-seeded Elena Rybakina, the reigning Wimbledon champion who won the title at Indian Wells last weekend, fired off 10 aces and made short work of Elise Mertens of Belgium 6-4, 6-3. Rybakina will face Martina Trevisan of Italy in the quarterfinals.
Trevisan eliminated Latvia's Jelena Ostapenko 6-3, 6-3.
The Associated Press contributed to this report.