NEW YORK – Second seed and 2012 champion Andy Murray crushed Bulgaria’s Grigor Dmitrov, 6-1, 6-2, 6-2 to reach a sixth US Open quarterfinal, clocking up a personal fast serve record in the process.

The 29- year- old reigning Wimbledon and Olympic champion stormed to an impressive seventh win in 10 meetings against the 22ndseeded Dimitrov.

From the moment Murray broke for a 3-1 lead in the first set, on the back of a lung-busting 32-shot rally, the outcome of the Arthur Ashe Stadium clash was never in doubt.

For good measure, Murray sent down his fastest ever serve of 141mph (226.9 km/h) at the end of a set where he allowed Dimitrov just five points on his service.

“I once hit a 145mph serve in San Jose but they recalibrated the machine the next day so it didn’t count. Tonight was the first time I have gone above 140,” said the 29-year-old. “It was lucky and I doubt I’ll ever do it again.” Dimitrov broke only once in

the match in the fourth game of the second set but it was a brief respite as Murray quickly reclaimed it before taking 10 of the next 12 games to seal the rout.

Dimitrov committed 43 unforced errors as Murray set up a last-eight clash with Japanese sixth seed Kei Nishikori, the 2014 runner-up who downed 37-year-old Ivo Karlovic, 6-3, 6-4, 7-6 (7/4).

Karlovic fired 21 aces in the contest but Nishikori’s 44 winners and a miserly seven unforced errors proved the key.

“It’s never easy facing someone serving like Ivo, never easy to return those kind of serves,” said Nishikori.

“But I tried to stay down. I have been returning well, so that also helped today. I think I played one of the best matches – serve, return, groundstrokes.”

Juan Martin del Potro, the 2009 champion, became the lowest ranked player in 25 years to reach the quarterfinals. (AFP)