World No 1 Elena Rybakina reached the quarterfinals of the Ningbo Open on Thursday on her return from injury when opponent Polina Kudermetova retired.
The top seed and defending champion was cruising 5-0 in eastern China when the world number 105 from Uzbekistan called it quits because of injury.
Moscow-born Kazakh Rybakina will face Poland's unseeded Katarzyna Kawa in the last eight.
Rybakina, 27, won the US Open for her third Grand Slam crown in September and usurped Aryna Sabalenka as world No 1 in New York.
She was then stunned in the second round in Beijing at the start of this month, and pulled out of the Wuhan Open citing a foot injury.
"Definitely not the way I wanted to finish the match," Rybakina, also the reigning Australian Open champion, said of the injury to Kudermetova.
"There is always room to improve and we'll see how the next one is going to go."
She added: "I'm just happy being here in Ningbo again, remembering the previous memories, and hoping that I can finish the year strong and be at my best."
SHNAIDER OUSTS EALA
Alexandra Eala crashed out in the last 16 as the Philippine history-maker suffered a battling straight-sets defeat to Diana Shnaider.
The Russian world number 13 won 7-5, 6-4 and will face the talented American teenager Iva Jovic in the quarterfinals.
The 21-year-old Eala in August became the first player from the Philippines to win a WTA title and is typically followed by a throng of fans from her country.
But after beating France's Diane Parry in straight sets in the previous round in Ningbo, the world number 20 came up against a far sterner test in Shnaider.
The 22-year-old Russian, who is seeking to win a sixth WTA singles title, used her superior power to take the first set in just over 50 minutes.
The second set was closer as Eala fought for survival.
Shnaider put the Eala serve under severe pressure in the ninth game before breaking for 5-4, then doggedly held to seal victory in one hour and 55 minutes.
The 18-year-old Jovic defeated two-time Grand Slam finalist Jasmine Paolini of Italy 6-4, 6-3.