The Madrid Masters is consigned to history now but the tournament proved to be a familiar tale for world No.3 Novak Djokovic. The Serbian wasn’t the only big name to fall early, but it’s his lack of tournament success in recent months that has been most surprising.

The question is: Why has Djokovic seemingly struggled (relatively) to hit the heights that we have come to expect of him since his last tournament victory at the Rome Masters? This past week Novak has provided us with his own assessment on why he has not been racking up more titles and playing with the confidence and assurance that was so evident in the first half of the year.

Before we take a closer look at Djokovic’s season it’s worth noting some other bits and pieces that transpired in Madrid. For one thing it’s the last time you’ll see the Madrid Masters played indoors, from next year the tournament will be moved to clay - and you can be sure world No.1 Rafael Nadal will have no problem with that change.

Nadal fell in the semi-finals after a three-hour-plus battle with Gilles Simon amid reports that Nadal was struggling with a shoulder injury and nursing his way through the event. After an almighty tussle that had the crowd, not to mention the players, exhausted, it was the Frenchman who prevailed in a deciding set tie-break. Simon still has hopes of ending the season at the Masters Cup in Shanghai and this run to the final significantly boosted his chances.

For Nadal it’s Paris next, followed by Shanghai and then the not so small matter of a Davis Cup final against Argentina in Mar del Plata, who will be led by David Nalbandian and Juan Martin del Potro. Speaking of the Argentine duo, they faced off in Madrid - as they did the previous year - but this time the result was reversed. Then it was Nalbandian who was victorious and went on to win the title, but this time Del Potro got the better of his compatriot before falling to Roger Federer in the last eight.

And, of course, a word for the new Madrid champion – Andy Murray. The Scot has now won back-to-back Masters Series titles and is currently in St Petersburg looking to defend the title he won there last year. If you’re a Murray fan you have to be delighted at his success this year and if you’re purely a neutral looking on you can’t but fail to be impressed by the progression he has made this year.

For a few years we’ve had the "big two" of Federer and Nadal and from late last year Djokovic joined the party to increase the crowd to three. Murray is now part of that elite group of four and, by this time next year at the latest, I’d expect that elite bunch of four to be extended to five thanks to the continued development of Del Potro.

This brings us back to Djokovic; his third-round exit to Ivo Karlovic in two tie-breaks came as a surprise purely because Djokovic failed to show the patience and composure needed on the big points that were always going to define the match. It was an impatience that has become evident in his game over a number of months.

First we have to put Novak’s season in context – it has been, for the most part, excellent. If the season ended today he’d have an Australian Open title, two Masters Series titles and an Olympic bronze medal to his name. However, if we are searching for why Djokovic has not achieved even more this season we’d look to his three defeats in finals and the five times he has been ousted in the last four of events. These late-round defeats have been consistent since his last tournament victory in Rome in May.

Djokovic believes he knows why he has not delivered at the business end in recent months: “Physical strength is something I’ve been trying to focus on lately,” the 21-year-old Serb told the Associated Press at the Madrid Masters. “I’m aware that this has been one of my issues in that I haven’t been recovering well from long matches and long tournaments.”

If it’s purely a physical issue which Djokovic is aware of and working on, then we will no doubt see a reflection of that over the course of the next 12 months. On the other hand, I wonder whether it’s more than a purely physical issue. Without question it’s a telling factor but then there is also the mental side of the game which takes its toll.

Djokovic is no longer under the radar in any sense of the word - as with Nadal and Federer, he is expected to succeed week in, week out. He sees the mental side of his game as one of his strengths and, in comparison to the tour at large, he is absolutely right. But as recent results suggest he has come out on the wrong side of battles with Nadal, Federer and Murray this season, winning only one of his last nine meetings with those players.

Following some time off after Shanghai to recuperate, I fully expect to see Djokovic firing on all cylinders early next year. The real test is whether he’ll still be firing 12 months from now.

How would you look at Djokovic’s 2008? A great season, or one that could have delivered so much more? And what changes, if any, do you think he needs to make to continue his charge at the top of the sport?