Djokovic roars into U.S. Open fourth round NEW YORK (Reuters) - Top seed Novak Djokovic roared into the fourth round of the U.S. Open with a 6-0 6-2 6-2 victory over Joao Sousa of Portugal under the lights of Arthur Ashe Stadium on Sunday. The 26-year-old Serb, who has yet to lose a set, smacked 34 winners to just 10 for the 95th-ranked Sousa in the 100-minute rout. Australian Open champion Djokovic faced just two break points in the match leading to one service break, while converting eight of 13 against his opponent. Djokovic said his top priority was winning as quickly as possible, but found some time to fine-tune his net game. "I am not obviously as comfortable on the net as I am on the baseline, but I've been working on it," said the world number one, who won 22 of 30 points he contested at the net. It's part of my game that I still need to improve. I'm aware of that. Djokovic said he was also putting in extra time with his serve. "It makes me happy that I have room for improvement, and I keep on spending hours and hours on the court and working on variety in my game," he said. And serve, especially that part of my game. I want to try and get as many free points on the serve as possible. Djokovic, a 2011 winner at Flushing Meadows who fell to Andy Murray in five sets in last year's final, next faces 43rd-ranked Marcel Granollers of Spain. Reporting by Larry Fine; Editing by Ian Ransom