Novak Djokovic moved within four matches of completing the first men's singles calendar-year Grand Slam in 52 years while top-ranked Ashleigh Barty was ousted by a stunning fightback from American Shelby Rogers. World number one Djokovic defeated Kei Nishikori 6-7 (4/7), 6-3, 6-3, 6-2, taking his 17th consecutive victory over the Japanese star and improving to 18-2 in their overall rivalry. "I was very pleased with the focus," Djokovic said. "Maybe at some points I wasn't my best, but I was determined and focused and that made the difference."
With a fourth career US Open trophy, Djokovic would complete the first men's singles sweep of major titles in the same year since Rod Laver in 1969.
Djokovic marched toward a 21st career Grand Slam title, which would break the deadlock for the men's record he shares with Rafael Nadal and Roger Federer, both absent with injuries.
The 34-year-old Serbian star advanced to a fourth-round matchup on Monday against 99th-ranked US wildcard Jenson Brooksby.
"He was playing pretty solid," Nishikori said. "I couldn't break the wall. Very unfortunate I lost."
Djokovic, who had 52 unforced errors and 45 winners, dropped the last three points of the first-set tie-breaker, the last on a Nishikori service winner.
"I don't think I started off very well," Djokovic said. "I was too passive. He was dictating the play. I was still trying to find the tempo. It took me a little bit of time to adjust to his game."
But Djokovic broke early in each set from there to seize command. In the fourth he grabbed a 3-2 lead and never dropped another game.
"Big credit to Kei, who played on a very high level," Djokovic said. "He was quick. It was tough. Great fight from him."