Novak Djokovic has reached the last four of the Miami Open with a straight-sets victory over sixth seed David Ferrer in Key Biscayne.

Ferrer stunned Djokovic early on with fierce returns before breaking the Serb in his opening service game.

The Spaniard continued to hit punishing ground strokes as his aggressive approach appeared to pay off in the opening stages.

However, the world number one was able to hit back in the seventh game of the set, forcing a break against the Ferrer serve.

Djokovic then broke again before sealing the opening set 7-5.

The Australian Open champion achieved another break early in the second set as he looked to take control of the match.

Ferrer then managed to break back in the 10th game after winning one of the longest rallies of the match.

However, Djokovic dug deep to break back in the next game and was able to wear down the world number seven to reach the last four.

He now faces John Isner in the semi-final after the American beat Kei Nishikori.