Over the past two months, Andy Murray has shown the tennis world just what he is capable of.

The 21-year-old Scot has won two Masters Series events in Cincinnati and Madrid and also reached the US Open final. He has defeated the world's top three players, Rafael Nadal, Roger Federer and Novak Djokovic, during this successful period of the season and has risen to a career high of No.4 in the rankings, qualifying for the first time for the end-of-season Masters Cup finale in Shanghai, China.

So how much further can Murray go? Can he be a realistic challenger to Federer and Nadal for that ATP No.1 spot and challenge for major honours? I definitely think so.

The Shanghai tournament is a great way to show how far Murray has come over the past year. He will mix it with the world's top eight players of the season and there will be nowhere to hide if he fails on the big arena.

I am sure Andy won't let down his growing number of fans and with the confidence he has built up over the past few months will look not only to be competitive in China but even, dare I say it, challenge for the title and move even closer to the world’s top three next season.

Murray has closed the gap on Djokovic considerably in the latter half of the 2008 season - from over 3,000 points difference in July to now just over 1000. The Brit hasn't got too many points to defend at the beginning of 2009 with the exception of tournament wins in Marseille and Doha. He has big opportunities to gain points in larger Masters series events in the USA and most of the clay-court season, a surface where he failed to reach the quarter finals in any tournament this year.

In contrast, Djokovic is defending his Grand Slam title in Australia in January as well as his Masters Series crown in Indian Wells in February. He also had a very good clay-court season this year, winning the Masters Series in Rome and achieving semi-final appearances in Hamburg, Monte Carlo and the French Open.

Unless Novak has another brilliant start to 2009, Murray could see himself as the world No.3 before too long.

However, the young Serb is improving all the time, too, and is capable of defending his titles with the skill he has. Federer and Nadal are also not too far away in the rankings to be caught throughout the season and all four of the world’s top players will need to be at their very best in every tournament.

This makes for an exciting 2009 season and the rankings could well move around throughout the year, showing the depth in men's tennis at the moment.

There are a number of new stars also trying to make their mark, including Juan Martin del Potro, Marin Cilic, Gael Monfils and Jo-Wilfried Tsonga, to name a few. They have all had impressive seasons in 2008 and if they stay injury free could challenge in some of the major tournaments and make even bigger names for themselves.

Del Potro should be especially watched, having won four tournaments and reached the US Open quarter-finals in recent months. He has very few points to defend at the start of next season and could find himself in the world’s top five before long, thus continuing the strong tradition of Argentinian tennis players over the past few years.

So even before the 2008 season ends, tennis fans should be excited and enthusiastic for 2009. The competitive nature and skill of the world’s top players makes for an intriguing season to come. Let’s just hope Murray ends Britain's long wait for a Grand Slam champion and maybe a No.1 ranked player. Who knows?