Former champions Andy Murray and Novak Djokovic have punched their fourth-round tickets at the US Open with relatively comfortable victories.

World No.1 Djokovic blew past Sam Querrey 6-3 6-2 6-2 on Saturday to book his spot, while Murray did things a little bit tougher.

“Sam is big server, very powerful. But he doesn’t move that well so I wanted to keep him moving around the court, mix up the pace and get as many returns as possible back,” said Djokovic after an 85-minute win which was never in doubt from the time he raced into a 5-0 lead in the first set.

Serbia’s Djokovic, the 2011 champion who is bidding to reach a fifth straight Flushing Meadows final, needed only 85 minutes to dispatch Querrey, leaving John Isner as the only American man remaining.

Britain’s Murray, seeded eighth, looked in cruise control early before gritting his teeth for a 6-1 7-5 4-6 6-2 victory over Russia’s Andrey Kuznetsov.

“I got off to a good start and then had a cushion when he got back into the match in the third set,” said 27-year-old Murray.

He will face either ninth-seeded Frenchman Jo-Wilfried Tsonga or Spain’s Pablo Carreno Busta for a place in the quarter-finals.