The morning after proves to be the enemy for Murray

Murray shows his torment on the way to a 6-1, 5-7, 6-3, 6-0 defeat by Nikolai Davydenko

Mornings and Andy Murray have never been the best of marriages and by midday here yesterday the Scot's relationship with this year's US Open was over. Resuming two sets to one down against Nikolai Davydenko after the previous day's rain had interrupted their fourth-round match, Murray failed to win another game. The British No 1, on court for another 36 minutes, lost 6-1, 5-7, 6-3, 6-0.

Murray said that it was the best set of tennis he had ever faced. Davydenko played immaculately, his relentless ground strokes pounding Murray into submission. The 25-year-old Russian, through to the quarter-finals here for the first time, is one of the more anonymous figures on the men's tour but he is not world No 6 for nothing.

Nevertheless Murray, having to start at 11am for the second day in succession, did not do himself any favours. Three double-faults in the opening game put him on the back foot and he failed to build on a 30-0 lead in the second.

Generally playing with caution, Murray tried to keep the rallies going in the hope of forcing mistakes, but Davydenko rarely faltered. When Murray did go on the attack he struggled to find his range, making 13 unforced errors in the final set to Davydenko's eight.

Luck was not on Murray's side, either: he was hitting a winner at 15-15 in the third game when a ball fell out of his pocket and the point had to be replayed. Davydenko won it and went on to break serve on a double-fault for the second time in a row.

Murray had points to win each of the next three games but was unable to take them. It had been a similar story the previous day and his failure to convert two points for a double break at the start of the third set may have been crucial.

While Murray has no intention of matching his new coach's daily routine ­ Brad Gilbert is a famously early starter who sometimes rises at 2am ­ the Scot acknowledged that he had to be better prepared for early matches.

"I normally sleep late and wake up late, so it was a bit different for me going to sleep at 10 o'clock and getting up early," Murray said. "He [Davydenko] started better than me both days.

"That's something that I have to learn from. And when it happens next time, I may have to try to do things a bit different to get myself ready. I'm not used to going on at 11 in matches. Maybe I need to practise at 9 o'clock in my practice weeks to try and get ready for matches like this."

Despite failing to reach his first Grand Slam quarter-final, Murray was far from downhearted. He has had a fine summer and the two-month-old partnership with Gilbert is already paying dividends.

In 18 matches under the 45-year-old American, Murray has beaten Roger Federer, lost on only four occasions, played in the last 16 of the US Open for the first time, reached the semi-finals and quarter-finals of two Masters series tournaments and made the final of another. Having climbed to No 19 in the world rankings, the Scot expects to move up two more places next week. He does not have many points to defend between now and Wimbledon next year, which will give him the chance to climb higher.

Murray said that the two remaining Masters series tournaments, in Paris and Madrid, would be key targets, particularly if Federer or Rafael Nadal misses either of them. He also said that he had not given up hope of making the eight-strong field for the end-of-season finale, the Tennis Masters Cup in Shanghai.

"I'm not going to walk away from this tournament with negative thoughts, " he said. "This has been the best summer of my life. I've always said you can play a couple of bad sets, but that's the thing, with age and experience, you get better at.

"A lot of young players can play well for a few weeks and then they'll have a few bad weeks, but I've kept it up. Since Wimbledon, I've won at least three matches in every tournament, which is a really good record.

"I'm so excited now because I think my serve can get much better, my movement can get better, I can get fitter, I can improve my volleys, my slice. Mentally I can get stronger.

"If I've got so many things to work on and things that can get better, then I can't wait to work on all those things with Brad."

Elsewhere, Roger Federer maintained his record of not dropping a set when he beat France's Marc Gicquel. Davydenko now plays Tommy Haas, who beat Marat Safin.

Safin's sister, Dinara, lost in straight sets earlier in the day to Amélie Mauresmo. The world No 1 meets the winner of Maria Sharapova and Tatiana Golovin in the semi-finals. Justine Henin-Hardenne beat Lindsay Davenport and plays Jelena Jankovic in the last four.