US Open: I didn't give Grigor Dimitrov a chance, says Andy Murray

Britain's Andy Murray clenches his fist after winning a point against Grigor Dimitrov, of Bulgaria (Picture: Darron Cummings/AP).

Murray produced a flawless display against the Bulgarian to win 6-1 6-2 6-2 and next faces Japan’s Kei Nishikori at Flushing Meadows for a place in the semi-finals.

The British No 1 had been out of sorts in the previous round, when he had to battle past Italy’s Paolo Lorenzi, and it seemed fatigue might be catching up with him at the last grand slam of the season.

Dimitrov, however, ran into one of Murray’s best performances of the year and the Scot believes he is now back on track ahead of the quarter-finals.

“I’ve not been sleeping great since I’ve been here. I don’t know why,” Murray said.

“On Sunday night I tried to get in bed early and I slept for 12 hours straight. I never do that. I never sleep that long. I went to bed very early.”

Murray added: “Grigor played his best, but I didn’t really give him a chance to get into the match. That’s the beauty of an individual sport. Just because you play badly a couple of days ago doesn’t mean I’m going to play badly [in the next match].”

Angelique Kerber took another step towards becoming world number one as she sailed past Roberta Vinci to reach the US Open semi-finals.

Kerber will snatch top spot away from Serena Williams if she equals or betters the American’s performance at Flushing Meadows and she turned up the heat with another ruthless victory.

The German beat Vinci 7-5 6-0 in Arthur Ashe Stadium and will next face either Caroline Wozniacki or Anastasija Sevastova for a place in Saturday’s final.