World number one Novak Djokovic has reached the semi-finals of the Miami Masters with a straight-sets win over a determined David Ferrer.

The defending champion was in frightening form in the opening set as he broke the Spaniard twice on his way to taking it 6-2.

The Serbian started the second strongly as he broke Ferrer's first service game, but the world number five put in a typically dogged display to break his opponent back instantly.

Both players then held serve as the hustling Ferrer was more than equal to Djokovic's powerful play from the back of the court.

The Australian Open winner found a break at 5-4 to put him on serve for the match, but Ferrer then broke again when he saw off Djokovic with a deft volley at the net.

The pair managed to hold serve again as the set moved into a tie break.

Djokovic kept his cool in the tie break as he broke Ferrer three times on his way to a 7-1 win.