Novak Djokovic has revealed that he was 'unsure' whether he would defeat David Ferrer in straight sets in the Australian Open quarter-final.

The defending champion claimed a 6-4 7-6[4] 6-1 victory over his Spanish opponent to reach the semi-final of the tournament.

"It was a great match," said Djokovic. "We played almost three hours. Already after a couple of games I was feeling 'wow this is going to be a long night'.

"It was big mental advantage to go two sets up. You have to hang in there, especially with a player like Ferrer. He's somebody who has great fighting spirit and never gives up.

"I was definitely not sure if I was able to prevail in straight sets. Momentum was on my side, I managed to step it up and I was very aggresive and it paid off."

The world number one will play British hopeful Andy Murray in the semi-final in Melbourne.