By Julian Linden
NEW YORK (Reuters) - World number four Andy Murray is already familiar with the added burden of expectation as he has long carried the hopes of a British nation counting on him to snap a 75-year grand slam drought.
Murray, vying to become Britain's first grand slam champion since Fred Perry won the U.S. Open in 1936, may have his best shot yet but his quest now carries an added challenge.
After two days of persistent rain halted play at the last grand slam of the year, Murray now faces a physical and mental test of having to possibly play four matches in five days before he can be crowned champion.
He will only get a day off if he makes the final, which tournament organizers earlier decided would be played Monday instead of the originally planned Sunday.
Murray came through the first of those four matches in great style Thursday, thumping American wildcard Donald Young 6-2 6-3 6-3 in under two hours.
It was sweet revenge for the Scotsman after he was beaten by Young in their only previous meeting, earlier this year, when he was struggling with his form and confidence.
"It was a tough moment for me," Murray said. "Obviously, not only are you playing badly, but you're not happy either when you're playing like that."
Things have gone much better for Murray since then and he is reaching his peak at the right time at one of his favorite tournaments.
His next opponent is John Isner, the towering American with one of the most lethal serves in the game.
"He's got a huge serve and can hit big forehands and is a little bit erratic and doesn't give you much rhythm," Murray said.
Isner, seeded 28th, reached the quarter-finals for the first time with a 7-6 3-6 7-6 7-6 upset win over Frenchman Gilles Simon but was expecting a tougher match from Murray.
"I played him in the Australia Open in 2010 and he beat me pretty easily," Isner said. "He would kind of take the air out of the ball and hit a lot of short angles and got me moving.
"I'm going to have to change a couple things up. He's one of the best returners in the game, so I'm going to have to serve my best. When I do get my chances on the return, I will have to take them."
(Editing by Frank Pingue)