Juan Martin del Potro spoke of his surprise that he would be facing Marin Cilic in the US Open quarter-finals and Andy Murray.

Britain's Murray, a finalist at Flushing Meadows 12 months ago, crashed out of the final grand slam of the year in a straight sets defeat to the Croatian 16th seed, describing it as the most disappointing loss of his career.

Argentina's del Potro, meanwhile, cruised into the last eight with a 6-3 6-3 6-3 win over Spain's 24th seed Juan Carlos Ferrero, setting up a showdown with the 6ft 6ins Cilic, who will be making his first appearance in a grand slam quarter-final.

"Cilic has everything to be a good player," del Potro said. "But Murray is number two, winning everywhere.

"So maybe everybody is surprised but Cilic has very good weapons. If he beat Murray he's confident and it will be a very tough one for me."

Murray will vouch for that as he failed to reach the levels of play that had earned him five ATP Tour titles in 2009, Cilic romping to 7-5 6-2 6-2 win at Arthur Ashe Stadium.

Asked if the defeat was the biggest disappointment of his career, Murray replied: "My tennis career, yes. I mean, worse things have happened to me, that's for sure.

"In terms of tennis I guess it's just kind of the way the match went that really makes it disappointing."

Murray had failed to get his game going on his preferred hard court surface at his favourite grand slam of the year but he refused to blame an injured left wrist for his defeat, having been sighted sporting a bandaged left wrist as he arrived at the Billie Jean King National Tennis Centre on a cool, cloudy and breezy day in New York.

"I had a problem with it for a week or so but regardless, I just struggled today," Murray said.

"I played poorly, I'm very disappointed, after the way that the last three slams went I felt like I had actually played well and lost..

"Today didn't feel like I played well."

Cilic had not beaten Murray in their three previous meetings but having saved two set points in the first set, he never looked back as the second seed wilted as quickly as the Croat's confidence grew.

"I had my chance in the first set and then struggled after that," Murray said. "I guess the momentum went with him and I didn't manage to get it back.

"I wasn't able to return well."

"I think that was the turning point," Cilic said of saving Murray's two set points. "It was a relief for me to settle into the game and after that I played very good tactically."

Cilic was also celebrating his first grand slam quarter-final.

"It feels really amazing," he said of his achievement. "This is my fifth time in the last 16 and my first time that I got through. I'm really happy about that now that I made that extra step.

"Hopefully I can go even further."

The sixth seed will have something to say about that. Del Potro was a last eight loser to Federer, who also beat him in the French Open semi-finals.

"Being in the quarters, it's important," del Potro said. "But it's a big difference past the quarters to the semis and then through to the finals.

"I was so close in the French Open to reach the final and to beat Roger.

"Here I have another chance to be better and I will try to go the semis. If I lose I still had a good tournament."

In the other quarter of the draw affecting Cilic and del Potro, third seed Rafael Nadal was set to play a night match against No.13 Gael Monfils of France while another Frenchman, seventh seed Jo-Wilfried Tsonga, was taking on Fernando Gonzalez of Chile, the 11th seed, in another late-starting contest.