World number two Andy Murray said he made too many mistakes, not only against Stan Wawrinka but throughout the week in London, to progress deep at the ATP World Tour Finals.
Murray failed to qualify for the season-ending semi-finals after going down 7-6 (7-4) 6-4 to Swiss fourth seed Wawrinka on Friday.
It was a winner-takes-all contest, with the victor assured of a final-four showdown against Roger Federer but the insipid Murray was no match for Wawrinka, who benefited from his opponent's error-riddled performance as he advanced to the semis for the third successive year.
"I felt like my timing would get better as the event went on, and it didn't actually, it got worse, which is strange," said Murray, who tallied 30 unforced errors in two sets at the O2 Arena.
"So that is nothing to do with not having enough time to prepare. Yeah, I don't think that's a valid reason.
"Way too many errors the last two matches. Everyone can make mistakes. It's just more on easy shots, cheap errors. Just something really for the most part of this year I haven't been doing.
"But this week and actually a lot of the time when I've played here on this court, I've felt the same way. I made too many mistakes. My timing wasn't there certainly the last few days. Maybe against David I had a little bit more time on the ball, whereas obviously Stan and Rafa hit the ball pretty big."
Murray will now turn his attention to Great Britain's Davis Cup final in Belgium next week.
Great Britain are contesting their first Davis Cup final since 1978.
The Scot added: "The only positive for me this week is I've come away from it injury-free. Now I have a couple more days to get ready for Belgium.
"Right now I'm not so much concerned about next week. I'm just disappointed that I lost the last two matches."