The third seed had hardly put a foot wrong in his first four matches but he made a bad start and never found anything like his best form.
Dimitrov took full advantage, his game as good as Murray’s was poor, and the Bulgarian showed his growing maturity to take control in the decisive moments at the end of the second set and win 6-1 7-6 (7/4) 6-2.
While Dimitrov moves through to his first grand slam semi-final against Novak Djokovic tomorrow, Murray must begin the inquest into what went wrong.
The worrying thing for the Scot is it is becoming a trend.
His break from the game to undergo back surgery is undoubtedly a factor but, since the ultimate high of beating Novak Djokovic to win Wimbledon 12 months ago, Murray has not beaten a top-10 player or reached a final.
In the last four grand slams, he has lost three times in the quarter-finals and once in the semi-finals and has managed to take just one set in all those matches.
This loss and his defeat by Stan Wawrinka at the US Open were particularly disappointing and Murray admitted he must find the motivation to get back to the top of his game.
The 27-year-old said: “I need to go away and make a lot of improvements in my game. I’ve lost a couple of matches in the last few slams where I’ve lost in straight sets and played poorly.
“So I need to have a think about things, what are the things I need to improve, and get myself in better shape and work even harder. Because everyone’s starting to get better. The younger guys are now obviously becoming more mature and improving all the time.
“I don’t feel like I have improved so much since Wimbledon last year, I think I’ve played some very good tennis but also some ordinary stuff at times.
“But if I’m going to play better tennis than I am just now, the only way to do that is by working even harder than I have before. Getting in the gym, getting stronger, becoming physically better.
“The only way that I can improve is by getting myself on the practice court and working harder than I have done in the last 12 months. Hopefully that will help.
“I still played some very good tennis this tournament. I’ve had a good run here at Wimbledon over the last few years. Obviously it’s disappointing for it to end like that.
“But now we’ll see whether I can come back stronger and come back better. No one knows, but I’m going to try.
“I still want to try to win more. I need to think forward and not backwards, and getting motivation from somewhere to try to get back to the top of my game.”
The day might have turned out very differently had Murray taken a break point in the first game, but he missed it and from the moment Dimitrov broke for 3-1, the champion was in trouble.
His big opportunity came at the end of the second set when Dimitrov had his first lapse allowing Murray to break back for 4-4.
But the Bulgarian held serve to force a tie-break and won the final three points with exemplary play.
Murray recovered from two sets down to win last year’s quarter-final against Fernando Verdasco but a repeat never looked on the cards and his reign ended with a whimper as he lost the final four games.
Murray managed a bow to the Duke and Duchess of Cambridge in the Royal Box and a wave to the crowd, who cheered their fallen hero. “I started the match badly and I think that gave him confidence,” said Murray.
“I should have done a better job of making it tougher for him. Also, when I got back into the second set, that was my opportunity there. He was the better player from start to finish.”
Murray looked nervous and leaden-footed but he insisted expectation was not a factor in his performance.
“I handled the pressure fine,” he said.
“I started the tournament well. I was playing good tennis. Today was a bad day from my side. I made many mistakes and then started going for too much and taking chances that weren’t really there.
“It was a tough day all around.” he added.