New York: Defending champion Rafael Nadal admits world number four Andy Murray will pose a significant threat to his US Open title when the two clash in Saturday's semi-finals.
Second seed Nadal cruised past 2003 champion Andy Roddick, the American 21st seed, 6-2, 6-1, 6-3 to reach the last four while Murray, the fourth seed, thwarted big-serving John Isner, the 28th seed, 7-5, 6-4, 3-6, 7-6 (7/2).
Top seed Novak Djokovic, who, like Murray, will also be playing in his fourth Grand Slam semi-final of 2011, will face five-time champion Roger Federer, the third seed, in Saturday's other semi-final.
It will be the second Grand Slam this year which has seen all four top seeds reach the semi-finals.
Nadal, who was a set down to Murray in the Wimbledon semi-finals in a match the British player was dominating, has a 12-4 career record over the fourth seed but is wary of the Scot's threat.
It will be their third Grand Slam semi-final clash of 2011 with Nadal winning at the French Open and at Wimbledon.
"If he's closer, he will beat me because on clay was very close, on grass was a very close match," said Nadal.
"He was beating me one set, and I remember an important mistake with an easy forehand, to go 40-15 in the beginning of the second. He's a fantastic player on all surfaces and it will be a very tough match for me."
Nadal, who became the youngest man to complete a career Grand Slam when he won here last year, will be playing in his fourth successive US Open semi-final.
Murray, who is vying to become the first British man since 1936 to win a Grand Slam title, said he thinks he can contend on the Flushing Meadows hardcourts.
He is also delighted to be part of the top four which has shared the Grand Slam and Masters titles between them this year.
"It's good for tennis. I think everyone has played great tennis in the slams this year," said the Scot.
"At the French it happened, and it nearly happened also at Wimbledon. Roger lost in the quarters. Rafa got injured at the Aussie Open. It's been very close to happening in almost all four of them, so it's been great consistency. Glad to be part of that."
Djokovic, who has already won the Australian Open and Wimbledon titles this year, made sure of his semi-final place on Thursday when Serbian teammate Janko Tipsarevic quit with an injury with the top seed 7-6 (7/2), 6-7 (3/7), 6-0, 3-0 to the good.
Federer eased past Jo-Wilfried Tsonga 6-4, 6-3, 6-3 to gain revenge for his shock Wimbledon quarter-final defeat to the Frenchman.
The 30-year-old Federer, who holds a record 16 Grand Slam titles, has every right to be confident going into Saturday's showdown.
His French Open semi-final victory over Djokovic in June brought an end to the Serb's stunning 43-match winning run, a streak which stretched back to December 2010 when he led his country to a maiden Davis Cup.
Despite Djokovic having lost just one further time, the Swiss star believes he has the weapons to repeat his Roland Garros heroics.
"It's pretty straightforward. I think we're both going to play aggressive. He's moving well. He's probably taken his game up to a higher level, but mostly in terms of confidence," said Federer.
"But I think when we do play against each other it's always exciting. We have great rallies. I like playing against him because it's a battle of the baseline.
"He's been having an amazing season, so it's a challenge right now in the men's game. That's what I like, who I like to play against."
Federer holds a 14-9 winning record over Djokovic and Saturday' semi-final will be the pair's fourth successive meeting at the last-four stage at Flushing Meadows.
Djokovic won last year's clash, saving two match points in a five-set thriller on his way to an eventual runner-up finish against Nadal.
Federer had won in 2008 and 2009 as well as comfortably seeing off Djokovic in the 2007 final when the Serb was far from the finished product that now dominates the men's game.
This will be their fifth meeting of 2011 and third in a Grand Slam semi-final.
Djokovic, who has 62 wins against two defeats all year, said his only concern was starting too slowly against Federer.
"I think I need to step on the court and just be close to the line, be more aggressive," he said.
"I think the last two matches I have been starting very slow. I'm very passive."