NEW YORK - Britain's Andy Murray advanced into his first Grand Slam semi-final with a gritty four-hour effort Wednesday, halting Juan Martin Del Potro's 23-match win streak to win a grueling US Open quarter-final.
The lanky 21-year-old Scotsman ensured a jump to a career-high fourth in the world rankings, matching the top mark of any man in British history, with a 7-6 (7/2), 7-6 (7/1), 4-6, 7-5 victory over the 19-year-old prodigy from Argentina.
"There were some intense moments but I was just glad to come through," said Murray. "He was on an unbelievable winning streak. He had confidence. I knew I was going to have to fight a lot, chance the pace of the ball.
"I was in the driver's seat. I didn't get too flustered. I kept my focus. I was happy with the way I came back."
Serving to force a fourth-set tie-breaker, Del Potro netted a forehand to give Murray two match points. Del Potro saved the first with a service winner but sent a backhand wide to end the drama after three hours, 58 minutes.
"I'm very relieved. I had my chances to put it away earlier and let it slip away," Murray said. "It feels great to be in the semi-finals. After a match like that it makes it feel even better."
Murray booked a Saturday date against the winner of a later match between American Mardy Fish and top-ranked Rafael Nadal - the Wimbledon, French Open and Olympic champion from Spain who is 5-0 against Murray.
Sixth seed Murray has won 17 of his past 19 ATP matches, losing only to Nadal in the quarter-finals at Wimbledon and the semi-finals at Montreal.
After titles this year at Doha, Marseille and Cincinnati to give him six career ATP crowns, Murray matched Tim Henman and Greg Rusedski as the top-rated tennis men in British history.
Del Potro, the youngest US Open quarter-finalist since Andy Roddick in 2001, had his left knee repeatedly checked by a trainer but it was only the pain of defeat that left him in tears after the match.
"I was feeling pain in all my body," Del Potro said. "I just did my best. We gave the people a good match. Andy is in good shape. He worked hard. He was better. He did everything. I played one of he best players in the world."
Murray could relate to the sadness of Del Potro, the first player to win his first four ATP titles in a row after US Open tuneups at Stuttgart, Kitzbuhel, Los Angeles and Washington.
"When it ends it's pretty emotional and pretty tiring to keep winning matches like that," Murray said. "He's probably upset he had his chance to get back into the match and didn't take it. He was struggling a bit at the end."
In contrast, Murray was almost stoic after an emotional triumph. It was because he has unfinished business.
"I'm excited to be in the semi-finals but the tournament is still going. I want to try to win it," Murray said.
"I understand getting to the semis is a great achievement. I want to go a little bit further. Winning is what really counts."
It was something of a grudge match. In their only prior ATP meeting at Rome in May, Del Potro retired in the third set but only after Murray rebuked him for a comment about Murray's mother, who was cheering her son from the stands.
"A lot was made of what happened in the last match but I said it wouldn't make any difference," Murray said. "At the end of the match he said he was sorry for what happened before and I said he played a great match.
"There was a feeling of respect between us."
Murray won the last six points of the first tie-breaker and dominated the second despite being broken at love just before it began. Murray began with two forehand winners and three errant Del Potro backhands later was ahead to stay.
"I played the big points great in the first two sets," Murray said. "When I broke a string on my racquet, I served a few double faults, lost my rhtyhm a little bit. It would have been easy to get down on myself but I didn't."
Del Potro, seeded 17th, broke Murray in the penultimate game of the third set and held to force a fourth. Fatigue gripped both men as they exchanged four early breaks, setting the stage for Murray's breakthrough in the last game.
"He was struggling a little bit at the end, trying to finish points quicker," Murray said. "Once I got a two-set lead I felt sure I would finish it."