The Serbian was dominant in the first set in Miami and was poised to take the second in similarly brisk style when he broke at the start of the second.

Ferrer broke back, though, and he did so again as Djokovic served for the match having broken the Spaniard for a second time.

But the defending champion got the early mini-break in the tie-break and never looked back as he sealed victory in one hour and 53 minutes.

Very happy

"I am very happy," said Djokovic on www.espn.com. "The scoreline doesn't say much because you have to earn your points against him.

"Coming into Miami, I was confident. This is the best match I've played the last couple of weeks in the States."

Next Djokovic will face Juan Monaco, who celebrated his 28th birthday by crushing eighth seed Mardy Fish 6-1 6-3.

The Argentine's serve proved too much for Fish, who was surprisingly out of sorts in front of a partisan crowd.

The American did not threaten the 21st-ranked Monaco until breaking back to level at 3-3 in the second set.

However, that merely encouraged Monaco to step up another gear and close out the match in an hour and 22 minutes.

"I meant every shot that I played, I did. It was a perfect match for me," said Monaco.