Defending champion Andy Murray was knocked out of Wimbledon in the quarter-finals by American 24th seed Sam Querrey on Centre Court.

Querrey, 29, won 3-6 6-4 6-7 (4-7) 6-1 6-1 to become the first American to reach a Grand Slam semi-final since Andy Roddick at Wimbledon in 2009.

The Briton, 30, led by a set and a break but lost 12 of the last 14 games as he appeared to struggle physically.

The defeat means Novak Djokovic could overtake Murray as world number one.

Second seed Djokovic, who plays Tomas Berdych later on Wednesday, needs to win the title to return to the top of the rankings.

Murray looked on course for an eighth win in nine matches against Querrey when he led by a set and a break, but less than two hours later he was out, after the American fired down his 27th ace.

Querrey took his chance superbly, hitting 70 winners, 30 of them from the net as he attacked at every opportunity.

For Murray, it appeared that the hip injury that disrupted his build-up to Wimbledon had finally caught up with him.

After breaking serve to lead 4-3 in the second set, letting out a loud "come on!", Murray dropped serve twice in a row, his opponent firing a brilliant backhand to clinch the set.

Any thought that it was a momentary lapse from the champion disappeared when Murray was broken again serving for the third set, but he took the tie-break on his fourth set point and seemingly regained control.

In fact, it was Querrey who took command as Murray appeared underpowered and unable to move freely.

The Scot won just nine points on serve in each of the fourth and fifth sets, with an average serve speed down at just 108mph, allowing Querrey to tee off on the return.

The American played a magnificent point at the net to break for the eighth time, serving out the match after two hours and 41 minutes.

Analysis - 'It was pretty evident his hip had deteriorated'

Former British number one Tim Henman

You have to give Querrey credit for the level of tennis he played but obviously, there's a big question mark over what has been Murray's fitness over the past three or four weeks.

His hip is one of those things where you are hoping that, if you have got a niggle, it gets better as the tournament goes on but to see him in so much discomfort it was pretty evident that it's deteriorated, and movement is such an important part of Murray's game.

Any lack of movement is a hindrance physically but I think it's also a distraction mentally.

Murray was up a set and a break at 4-3 in the second set and you think perhaps he can take advantage of this and get two sets up, but you could see with lots of different movements he was certainly hobbling.

When he was trying to change direction, pushing off the compression in the the hip joint was uncomfortable. At this level and stage of the tournament you know you have got to be 100% fit or, if not, very close to it.

That was not the case with Andy, and it is very disappointing for him.