Miami Masters 2014: Andy Murray plays down controversial umpire incident after defeat to Novak Djokovic

Andy Murray was left to rue his failure to capitalise on several openings after old foe Novak Djokovic ended his Sony Open title defence.

World number two Djokovic gained a measure of revenge for his defeat to Murray in last year's Wimbledon final with a clinical 7-5 6-3 victory in their quarter-final encounter in Miami.

The 20th meeting between these two men was the first since the Scot triumphed in straight sets at SW19 and was tainted by controversy in the 12th game of the first set.

With sixth seed Murray serving, Djokovic advanced and appeared to play the ball before it passed over the net - which is against the rules.

The point stood and Murray seemed unable to put it to the back of his mind, making three unforced errors as Djokovic wrapped up the first set.

Although Murray made a confident start to the second set and broke Djokovic for a 3-2 lead, the Serbian hit back to win the last four games to move into the semi-final.

Murray admitted he failed to take his chances but took comfort in some aspects of his performance.

"I had many opportunities like 30-all games and 0-30s on his serve, and I didn't serve so well when I went ahead in the second set," Murray said on the ATP Tour website.

"I would have liked to have done that better, but I was hitting the ball better from the back of the court.

"I was playing aggressive. I was taking the ball early. I was trying to come forward a bit. My game is not far from where I want it to be."

As for the incident that left a cloud over the encounter, Murray told reporters: "It maybe had a slight bearing on that game."

Djokovic, meanwhile, was immensely satisfied by his straight-sets win over one of his closest rivals.

"That tournament win is very special for me from a mental point of view, because I have been struggling throughout the whole tournament," he said.

"That gives me even more confidence and self belief that I need in this moment."

Djokovic will face Kei Nishikori in the last four after the 20th seed rallied from a set and a break down to stun 2005 and 2006 champion Roger Federer.

The fifth seed won the first set with the minimum of fuss and claimed what appeared an all-important break in the seventh game of the second set.

Nishikori refused to accept defeat, however, and took the match to a decider, where the Japanese wrapped up a 3-6 7-5 6-4 victory in two hours and eight minutes.

In the women's action, second seed Li Na edged out Caroline Wozniacki in two tight sets to move into the semi-final.

The Danish 11th seed looked on course to take the match to a decider after taking a 5-3 lead in the second set, but lost the last four games as Li sealed a 7-5 7-5 success.

The Chinese will next play 10th seed Dominika Cibulkova, who hit back from a set down to defeat Agnieszka Radwanska 3-6 7-6 (7/5) 6-3, in a repeat of this year's Australian Open final, which Li won in straight sets.