New York — Stung by dropping the first set to an unseeded opponent, top-seeded Rafael Nadal swept imperiously through the next three to beat Mardy Fish, 3-6, 6-1, 6-4, 6-2, on Wednesday and reach the semifinals of the U.S. Open for the first time.

Forced to wait until 11.30pm local time for his match to start, and surprised by the spirited start by the American in front of his home crowd, Nadal dominated thereafter to set up a semifinal against Andy Murray of Britain.

“This is one of the things that we players discuss all the time. There should be a limit on when to start. But we know that the TV rules in this,” Nadal said.

“I think I’m going to end up sleeping at 5 a.m. I’ve got to go eat. With all the attention on the match, it takes a while to unwind. There’s nothing else you can do.”

The sixth-seeded Murray prevailed earlier in a tight struggle with Juan Martin del Potro, beating the Argentinian 7-6 (2), 7-6 (1), 4-6, 7-5 to reach his first grand slam semifinal.

Serena beats sister Venus

In the women’s draw, Serena Williams rallied from a break down in both sets to edge big sister Venus 7-6 (6), 7-6 (7), while Russian Dinara Safina comfortably beat Italian Flavia Pennetta 6-2, 6-3.

Nadal, who has won four titles at the French Open and one at Wimbledon and had usurped Roger Federer as the world’s No. 1 player ahead of this final grand slam of the year.

Fish took the opening set on the strength of a 23-6 edge in winners and one service break, but the powerful Spaniard never faced a break point the rest of the way.

Murray ousted del Potro, who had never advanced farther than the third round in a grand slam before. The Argentine had never won a tournament before July, then ripped off four straight titles to soar up the rankings. His run of wins on tour was second only to Nadal.

Murray, playing in the quarterfinals for a second straight Grand Slam tournament, repeatedly won points with drop shots. His ranking, already a career high, will now climb to No. 4, matching the highest ever for a British man in the rankings’ 35-year history.

Murray’s nerves showed at times. Serving for the second set, he lost the game at love. But he loosened back up to easily win the tiebreaker.

The Scot was up a break in the third and the match seemed close to over. But a string of mistakes by Murray seemed to revive del Potro, who had his knee strapped during the match, and he forced it to a fourth set.

Fourth-seeded Serena Williams barely got the better of Venus Williams in a quarterfinal that was fit for a final, coming back to win and go one up in their head-to-head history.

In the semifinals, Serena will meet No. 6 Safina, who advanced earlier in the day by overpowering No. 16 Pennetta. The No. 2 and title favorite Jelena Jankovic of Serbia will face Russian No. 5 Elena Dementieva in Friday’s other semifinal.

The seventh-seeded Venus had all sorts of chances to take control. In the second tiebreaker she could not convert on four set points. /AP