Andy Murray brushed off recording the fastest serve of his career, saying it was down to luck and he doesn't expect to do it again.

The Scot, who cruised to the quarter finals of the US Open, achieved his new personal best with a serve of 141 miles per hour to win the opening set in New York.

Murray says he is proud of his latest tennis achievement but is concentrating on the wider success that will see him progress to the last eight of the competition.

He delivered a resounding message about his credentials to win the US Open after cruising past Grigor Dimitrov with a flawless performance in Arthur Ashe Stadium, winning 6-1 6-2 6-2.

"I played extremely well, tactically I played a good match," Murray said. "It's definitely up there, I played well today, made very few unforced errors and made it tough for Grigor."

"I served one at 145 in San Jose once but the next day they recalibrated the gun because it was completely wrong.

"Tonight's was the fastest serve I've hit. The other one was here at the US Open, 138. I think it was lucky. I only did it once. I'm not expecting to do it again."

The British number one has now reached the last eight in 22 out of his last 23 grand slams and he will face Japan's sixth seed Kei Nishikori for a place in the semi-finals.