Novak Djokovic extended his unbeaten start to the year as he set up a semi-final against new American number one Mardy Fish at the Sony Ericsson Open.

The Australian Open champion beat South African Kevin Anderson 6-4 6-2, gaining revenge for a shock defeat to the same unseeded player in their only previous meeting, three years ago at the same Miami event.

Djokovic saved five break points and held his serve throughout the match to clinch a clash with Fish in the last four.

The 23-year-old Serbian has now won his opening 22 matches of the year and is seeking a fourth title in 2011, having beaten Andy Murray, Roger Federer and Rafael Nadal in his three finals so far.

He is chasing his second Miami title, having won the event in 2007.

While Djokovic is enjoying a stellar season and stands at number two in the world, Fish, 29, has his own landmark achievement to celebrate.

The 29-year-old will overtake Andy Roddick to become the highest-ranked American after reaching the semi-finals by beating Spain's sixth seed David Ferrer 7-5 6-2.

He will climb to at least 11th place when the new lists are published next week.

Defending champion Roddick lost his opening match in Miami and will drop out of the top 10, with Fish becoming his country's top player for the first time.

‘I've never been in this position before. Obviously it's very humbling,’ said the 14th seed.

‘This is a pretty big country, a lot of people playing tennis. So I'll try to put it into perspective, and I will.

‘Career high number 11 sounds really good, too. These are the rewards that come with working as hard as I did.’

Fish has built up his fitness and worked hard on his game, and the 2004 Olympic tennis runner-up is seeing the benefits - not that he regrets anything about the early years of his career.

‘I was who I was when I was 21 and 24 and 23,’ he said.
‘There's just not one ounce in my body that goes back to the past. I had some really good results. I won a silver medal at the Olympics. There's not very many people that have done that.

‘I did a lot of cool things. I played a lot of good matches. You can't be as mature at 21 as you are now, as I am now. Never look back.’

The top 10 perhaps beckons for Fish.

‘That's a huge goal,’ Fish said. 'I've been pretty vocal about that basically since last summer. I'm close, I guess. Every match, every point that I get, that's the goal.’