Since 2009 we have talked about a "big four", more recently a "big four". Andy Murray, the best British tennis player for decades, was a well established member of the so called "big four". Recently, however, he has been ruthlessly jettisoned from this prestigious group as Djokovic, Nadal and the immortal Roger Federer have continued to raise the level of performance required to be part of the ultimate elite.
It would be harsh to say Murray has become worse, if anything he is a marginally better tennis player than he was three years ago. Murray hasn't been able to improve at a rate higher than that of the three protagonists above him. If Murray were to break into this leading group then his rate of development must be significantly higher than the top three in order to close the gap and eventually overtake them.
Inevitably there are other players vying to break into the world's top four, notably Jo-Wilfried Tsonga, Tomas Berdych and Juan Martín del Potro. Given David Ferrer is only a genuine threat on clay there seems no reason to include him. Tsonga, Berdych and del Potro all share similar characteristics; they are all extraordinarily powerful men and possess outrageous hand-eye coordination.
Del Potro won the US Open in 2009 and the entire tennis world was of the same opinion: this Grand Slam was the first of many. However, the giant Argentine suffered terrible wrist problems following his US Open triumph which caused him to miss vast chunks of the 2010 season. It has only been recently that we have seen the form he showed in 2009, notably taking two sets off Federer at the French open last week. He possesses one of the most destructive forehands on tour and with a reasonable serve to boot, he is a real contender provided he can stave off injury for a sustained period of time.
If there is a more charismatic person on tour than Jo-Wilfried Tsonga then I would love to know. The flamboyant Frenchman has long been a "talent", recently he has started to turn his scintillating natural talent into results. Although he squandered two match points at Roland Garros against World #1, Novak Djokovic, on his way to losing the match in 5 sets he showed glimpses of becoming the real deal. Such was his disappointment as he left Philippe Chatrier he was in tears. His performance in this contest had the French crowd and television audiences worldwide in awe of his shot-making ability. Expect big things from him for the remainder of the 2012 season.
Czech, Tomas Berdych, is one of the least popular players on the tour for two reasons. Firstly, by all accounts he isn't the most pleasant of individuals with both Nadal and Djokovic taking issue with Berdych's histrionics. On a more positive note, he is cataclysmically destructive on court - booming groundstrokes, a rocket serve and pretty deft touch for a big man at the net. He has all the components needed to challenge the elite.
On their day, all of the afore mentioned are capable of taking sets off the top 3 and beating Andy Murray. There are others who could easily have made this list, the record breaking John Isner, tennis's wonderkid, Milos Raonic, or even the enigmatic Richard Gasquet.
If Andy Murray isn't careful he shall be trying to propel himself back into the top four rather than trying to fight his way into the top three.