Defending champion Novak Djokovic has received his second straight walkover at the US Tennis Open, advancing to the fourth round after his opponent Russia's Mikhail Youzhny retired hurt.
Top seed Novak Djokovic cannot seem able to get a match at the grand slam, with Russian Youzhny retiring due to a leg injury when trailing 4-2 in the first set of their third round match.
Youzhny was treated during the changeover at 4-1 in the third-round match at Arthur Ashe Stadium and had his left thigh taped.
He won the next game on his serve but could not continue, giving Djokovic a pass into the round of 16.
The Serb, winner of this year's Australian Open and French Open to complete a career grand slam, came into the match off a three-day break due to a walkover into the third round when Jiri Vesely of the Czech Republic withdrew.
"It's difficult to pick the words now. I don't think I ever had this kind of situation in my career, where I had a second-round walkover and the third round 30 minutes only," Djokovic said on court before heading off to practice.
"I'll try to get the positives out of these six games. Obviously I did start very well with a good intensity and I'll try to carry that into the next match."
Defending champion Djokovic will next face either 20th-seeded American John Isner or 84th-ranked Briton Kyle Edmund with a berth in the quarter-finals at stake.
Djokovic, who has been bothered in recent months by a nagging wrist injury, won his opening match at Flushing Meadows on Monday, 6-3 5-7 6-2 6-1 over 247th-ranked Jerzy Janowicz of Poland.
Meanwhile, fourth seed Rafa Nadal showed he is healthy and ready to challenge for a third U.S. Open title as he rolled into the last 16 with a fist-pumping 6-1 6-4 6-2 win over Russian Andrey Kuznetsov.
Erasing any lingering concerns over an injured wrist that kept him out of Wimbledon, Nadal has made a powerful start to the year's final grand slam, racing into the fourth round without dropping a set.
It was vintage Nadal on a warm New York evening, as the energetic Spaniard wore down his 47th-ranked opponent with a breathless work rate and a bombardment of stinging forehands.
On the women's side of the draw, Germany's Angelique Kerber, crushed the 17-year-old American qualifier CiCi Bellis 6-1 6-1 to reach the fourth round.
Kerber is enjoying a breakout season that has her challenging for the world number one, while Bellis, the second youngest player in the women's field, had won three qualifying matches and beat two players within the top 65 before her dream run was ended by a rash of errors.
The second-seeded German took 55 minutes to close out the day five program at Flushing Meadows.
"Congrats to CiCi. She played a great tournament and for sure she will have a great future," the gracious Kerber said in an on-court interview at Arthur Ashe Stadium.
Next up for Kerber is Petra Kvitova of the Czech Republic, a 6-3 6-4 winner over 22nd seed Elina Svitolina of Ukraine.
Kerber and Kvitova have split their eight career meetings.