ANDY Murray suffered one of the most chastening nights of his career as he was humbled by Roger Federer at the ATP World Tour Finals.

Qualifying for the eight-man event at London's O2 Arena appeared to have ended Murray's troubled season on a high, but it certainly did not feel that way after a 6-0 6-1 thrashing.

Murray was two points away from losing 6-0 6-0 for the first time since he was a 16-year-old amateur playing on the lowly Futures circuit.

In a tournament of one-sided matches, Murray now has the unwanted distinction of having suffered the worst defeat since the event moved to London's O2 Arena in 2009, while it was his heaviest loss for seven-and-a-half years.

Federer was already guaranteed a spot in the last four and his display was proof once again that at 33 he is playing some of his best tennis.

But, as good as the Swiss maestro was, Murray was awful, and he made no attempt to hide his disappointment.

"It was a tough night," he said. "I've lost slam finals and stuff, which has been very tough. But in terms of the way the match went, it was not ideal from my side of the court - far from it.

"He played exceptionally well. That's for sure. I can say I'm disappointed with my level tonight. But if I played well, he probably still would have won anyway.

"Obviously, 6-0 6-0, that's never happened to me in my (professional) career. I think 6-0 6-1 has maybe happened once to me before. So it's very disappointing, especially in a match like that.

"I would have obviously hoped to have done a lot better than that. It wasn't what I was looking for when I went on the court.

"In terms of the nature of the match, when he's extremely loose like he was tonight, he was obviously through in the group, he was able to maybe try some shots that he might not try in other situations.

"But everything he tried tonight came off. He has the ability to do that."

Kei Nishikori's 4-6 6-4 6-1 victory over David Ferrer - who replaced the injured Milos Raonic - earlier on Thursday meant Murray knew he could not lose a set if he wanted to pip the Japanese player to a spot in the last four.

Nishikori said he would not be following the match because he wanted a "good dinner", and he would barely have tucked into his starter when his progress was secured after a first set that lasted just 24 minutes.

A packed crowd roared their approval for both players - Federer receiving marginally the more rapturous reception, as Murray probably knew he would.

Murray won the first two points on the Federer serve but then lost an epic rally and from there things unravelled in double-quick time.

From deuce in the second game, Federer won 14 points in a row to lead 5-0 and Murray managed only eight points in the whole set.

It was the first ever love set in the 23 matches between the pair, and all the more remarkable considering they had been tied at 11-11.

The second set was marginally more competitive but it was not until the 12th game that Murray finally got on the board only to succumb one game later with the match just 56 minutes old.

Describing what was going through his head, Murray said: "Just try and set a target of winning points.

"Try and win two points in a row rather than trying to focus on, 'Okay, I want to get this game'. You just try and set smaller goals than that.

"It's frustrating. That would be the one word that I would use to describe it. There's some matches you can maybe look on where you might have behaved badly, felt like you hadn't given your best effort or whatever, maybe be embarrassed about that.

"But I was trying tonight. I tried from the first point through until the last. So it's very frustrating when that's happening to you."