Andy Murray's primary emotion was relief as he reflected on one of the more remarkable victories of his career in the second round of the US Open last night.

Big-hitting Dutchman Robin Haase always looked a tricky assignment but no one could have foreseen the drama that saw Murray battle back from a poor two sets to take complete control, only for his opponent to nearly stage the most remarkable of comebacks.

The fourth seed won 13 games in a row to lead 4-0 in the fifth, with Haase looking out on his feet and struggling with pain in his right leg, but somehow he found the energy to win four games in a row only for Murray to take it on his third match point.

After his 6-7 (5-7) 2-6 6-2 6-0 6-4 victory, Murray said: "It was an unbelievable ending to the match. I'm just glad I'm in the next round and get a chance to improve and play better and give myself a chance."

While his fans may have been fearing the worst as the fifth set reached its conclusion, Murray, who qualified for the Barclays ATP World Tour Finals in London with his victory, insisted: "That's when I felt my calmest.

"Even when he started coming back, I wasn't panicking, I wasn't getting frustrated. I just stayed focused and managed to turn it around.

"It's just one of those matches where anything could have happened at the end. I just stayed a little bit tougher than him and got the win."

It was the sixth time in his career Murray has come back from two sets down, and he added: "It does help to know physically you can get through the match. That's really the main thing. You always feel like you can turn the match round in terms of the tennis."

The Scot now has a day off in which to work out how to avoid such drama when he faces Spain's Feliciano Lopez in the third round tomorrow.

While Murray survived yesterday, women's third seed Maria Sharapova did not, the Russian going down 6-3 3-6 6-4 to Flavia Pennetta of Italy.

The 2006 champion, who had been the second favourite for the title behind Serena Williams, paid for 12 double faults and 60 unforced errors.

Pennetta, who goes on to face China's Peng Shuai, said: "I think this one is one of the best victories in my career, and it is going to be like this forever."

Rafael Nadal and Juan Martin Del Potro had comfortable victories yesterday while today's order of play sees Caroline Wozniacki face Vania King and Roger Federer take on Marin Cilic before the heavyweight clash between Serena Williams and Victoria Azarenka.