When Andy Murray began as a professional tennis player in 2005, the Scot had two goals that he wanted to achieve in his career - win a Grand Slam title and become the world number one.

One of these was achieved on September 10, 2012 when Murray outlasted Novak Djokovic in a near five-hour showdown in the US Open final at Flushing Meadows as he ended Great Britain's 76-year wait for a male Grand Slam singles champion.

He continued his Major success by winning Wimbledon earlier this year, but after surgery on his troubled back brought an early end to 2013, is it possible for the 26-year-old to secure his second goal and become the best player in the world?

On the back of his success at SW19 in July, all of the talk was of Murray inevitably surpassing Djokovic at the top of the world rankings. It was regarded as only a matter of time, rather than something that would take even more dedication and hard work from the two-time Major champion.

But after Murray made the decision to end his season to undergo what was described as minor back surgery, it could be argued that his chances of ever being called the "world's best player" diminished at the same time because he has been left with no option but to chase Djokovic and Rafael Nadal for the whole of 2014.

Of course, there is no denying that the surgery wasn't optional because Murray has visibly struggled with his back after making the transition from different court surfaces, but with the rankings points that he will lose and what he has to defend early next year, it's going to be a tough ask for Murray to even break into the top two positions over the 12 months.

Murray could find himself as many as 8000 points adrift of Nadal after the conclusion of the ATP Tour finals, which is the same total that you would earn for emerging with all four Grand Slam titles over a calendar year, while Djokovic is also well out of reach.

That leaves Murray facing the likelihood of meeting either Nadal or Djokovic before the final of any Grand Slam and probably having to beat both players in the space of three days if he is to add a third triumph. It's something that he has never done in a major championship.

Murray's priority should initially lie with ensuring that he does not slip out of the top four because that would be where the bigger problems start. By the time next year's Australian Open comes round, his advantage over fifth position would have been cut dramatically with big points available over the next few weeks.

His cause is helped by current number four David Ferrer having a lot to defend, but while Murray will be focused on looking ahead rather than behind, it's important not to ignore the smaller picture when he returns because he needs to accumulate plenty of points before the middle of the year to ease the pressure of defending his Wimbledon title.

Roger Federer is the obvious proof of what could happen as soon as points begin to disappear at the top of the standings. The Swiss player is moving towards the end of the career, but the difficulty to maintain a high ranking after making the initial slip is evident with the 32-year-old now down to number seven with plenty of points to defend at the ATP Tour finals, if he manages to qualify.

As of yet, it's unknown how Murray will return from his enforced layoff, or whether Nadal or Djokovic can enjoy an injury-free year to further cement their current dominance, but it's a situation which could make Murray re-evaluate whether it's realistic to ever become world number one.

It's not as extreme as effectively starting his pursuit from scratch but defending points is almost more difficult than beginning with nothing. The pressure to have to repeat your previous year's performance can be tougher to deal with than entering a tournament with a free shot of attempting to reach the back end of a competition.

Murray has dealt with all kinds of pressure during a career that has witnessed as many highs as lows, and it's conceivable that this is just another obstacle that he can take in his stride to ensure that he does not completely lose touch with the upper echelons of the game.

But one thing is for sure - Murray is going to have to call upon all of the experience that he has picked up over the years to ensure that the sport can continue to have a "big three", rather than an "outstanding two".