By Will Swanton
NEW YORK, Sept 5 (Reuters) - American twins Bob and Mike Bryan had their calendar-year grand slam hopes dashed at the U.S. Open on Thursday and then said no duo will likely ever accomplish the feat again.
The top-seeded brothers, who won this year's Australian Open, French Open and Wimbledon men's doubles titles, fell 3-6 6-3 6-4 to Czech Radek Stepanek and India's Leander Paes in the semi-finals of the men's doubles at Flushing Meadows.
The hype surrounding the brothers' attempt to secure the first doubles calendar slam since Australia's Ken McGregor and Frank Sedgman in 1951 came to a halt after one hour and 51 minutes on Arthur Ashe Stadium.
"Realistically it will probably never happen again," Mike said. "The margins are just so fine in doubles. There are just too many great teams out there and too much can go wrong. A lot has to go right to be in that position."
The brothers, who became the most successful men's pair in grand-slam history in January when they won their 13th doubles title together at the Australian Open, said they were anxious in the lead-up to the year's final grand slam.
"I don't know about Mike, but I have had a tough time sleeping in the last couple of weeks," Bob said.
His brother added: "It's been in the back of your mind the whole way. Once you get out there, you try to put it aside. You win a set and then you're seeing that, okay, you're three sets away from a grand slam.
"Every point just becomes a little bit bigger, every moment. It makes it a little tougher."
Bob denied the pressure got to them. After cruising through the first set, they fell behind 1-5 in the third set before a comeback started too late.
"Once you get on the court you're just boom, game plan, focus. It definitely didn't get to us," said Bob.
"It was just that they hit some great shots. In one sense we're disappointed. In another sense, we're relieved and we can start the next chapter.
"We're competitors and we hate to lose, and we knew what was riding on this match. But it's a little bit of a relief when you get to exhale for the first time in a few months. (Editing by Frank Pingue)