Novak Djokovic has admitted that he isn't quite sure how he managed to overcome Tomas Berdych in their Wimbledon quarter-final this afternoon.

Berdych matched the world number one for large periods of the match and was two breaks up at one point in the second set.

However, Djokovic came back to secure a 7-6 6-4 6-3 win to reach the semi-finals, although he believes that Berdych could just have easily emerged victorious.

"It was a very close match, it could have gone either way," Djokovic told reporters.

"He could have won the first two sets, he had a double break in the second. I don't know how I managed to go ahead, I don't know how I turned it around. I am really happy with the performance. I am playing some of the best tennis on grass of my career.

"Tomas is a very powerful player. As you could see, we went toe to toe in the first set. It was a huge confidence boost to come back and go two sets up."

Djokovic's win sees him progress to the semi-finals, where he will face Juan Martin del Potro.