Defending champion Novak Djokovic racked up his 90th win at the US Open on Wednesday by defeating Serb compatriot Laslo Djere who retired in the third set of their second round clash.
Djokovic, a four-time champion at the tournament and seeking a record 25th Grand Slam title, was leading 6-4, 6-4, 2-0 when Djere called it quits.
The world 109, who pushed his countryman to five sets in New York last year, had required a medical time-out to treat an injury after dropping the second set.
The 37-year-old Djokovic had himself required a visit from the trainer for what appeared to be a side strain after sealing the first set.
World number two Djokovic is now the only man to have won 90 matches at all four Grand Slams.
"It's not what we want to see when there's a retirement. Laslo had an injury which took him off the tour for some time and he's been struggling to come back," said Djokovic.
"He's such a good player in these conditions and the second set should have been his, he was 4-2 up.
"I don't know if (my) winning the second set probably put more burden on him."
Djokovic will next meet Australia's Alexei Popyrin who he defeated at the Australian Open and Wimbledon this year.
Defending champion Coco Gauff shook off her struggles on serve to reach the third round of the US Open on Wednesday with a 6-4, 6-0 victory over 99th-ranked Tatjana Maria of Germany.
The 20-year-old American, who has had an erratic season since capturing her maiden major on the hard courts of New York, had nine double faults and put just 44 percent of her first serves in play in what she called an "annoying" match.
"I love Tatjana, her family. She's very annoying to play," Gauff said. "I think tonight was just an annoying match. The balls, you were able to hit winners on them, but because she's slicing it, you have to generate all the power.
Gauff escaped with the first set despite 20 unforced errors -- double the total of her 10 winners. She double-faulted on her first set point and had to replay the second when the electronic line-calling system malfunctioned.
Maria, a 37-year-old veteran, didn't have the weapons to take advantage, converting just one of her five break chances.
With a set in hand Gauff began to hit with more authority. She finished with 25 winners and 25 unforced errors and won the last seven games as she set up a third-round meeting with Ukraine's Elina Svitolina, who beat compatriot Anhelina Kalinina 6-1, 6-2.
