Djokovic on to quarterfinals

Novak Djokovic sweated his way to a 6-3, 6-4, 6-3 fourth-round win over Joao Sousa as the heat returned to the U.S. Open on Monday setting up a potential quarterfinal meeting with Roger Federer. Djokovic did his part, improving his perfect record in U.S. Open fourthround contests to 11-0 leaving it to Federer, who took on John Millman in Monday’s late contest on Arthur Ashe Stadium court to give the fans what would be a hotly anticipatedmatchup. Sousa, the first Portuguese player to reach the fourth round of any Grand Slam, had knocked off two seeded players, No. 12 Pablo Carreno Busta and No. 17 Lucas Pouille, en route to the last 16. The biggest concern for Djokovic might well have been the conditions as the heat returned to New York after a few days of relief. Through his opening round matches Djokovic and his play both suffered under a blazing sun and with temperatures once again nudging into the 90s, the extreme conditions took a toll on 31-year-old Serb. The sixth seed went off court two sets and 2-1 up for a medical evaluation. The 13-time Grand Slam winner had made easy work of the opening set, breaking Sousa twice, the second time to close out set. Things grew tougher in the second as a sluggish Djokovic labored before again clinching the set with a break. As the temperatures rose so did the tempers, both players engaging in animated arguments with chair umpire James Keothavong over points. Djokovic, however, was able to keep is cool just long enough to finish off Sousa with another late break.