Djokovic into US Open quarter-finals

Edmund, playing in a Grand Slam fourth round for the first time, barely got a look-in during the first two sets against the world number one and defending champion, who booked a last-eight meeting with ninth-seeded Frenchman Jo-Wilfried Tsonga, a 6-3, 6-3, 6-7 (7/9), 6-2 winner over American Jack Sock.

"Feels great to play a full match after a weird couple of days when I didn't have too much tennis," said Djokovic, who received a walkover into the third round when Czech Jiri Vesely pulled out of the tournament injured and played just six games before third-round foe Mikhail Youzhy retired.

Even with the extra rest, however, he required on-court treatment on his right arm -- the same one he had treated during his scrappy first-round victory over Jerzy Janowicz.

Having raced through the first two sets in just over an hour, Djokovic sought treatment after surrendering his first service break of the night -- starting a run of three straight games for Edmund that gave the Briton a 3-2 lead.

Djokovic put the set back on serve with a break for 3-3, and broke Edmund at love to close out the match.

Even after the tighter third set, Djokovic was pleased with his night's work.

"I came out of the blocks with high intensity which was hard after waiting all day to start the match," he said. "I made him work for every point.