What players must do to qualify for Shanghai
The mountaintop of men's tennis is a little more crowded than it's been in the past few years. The perennial Big Two of Roger Federer and Rafael Nadal morphed into the Big Three with the ascendancy of Novak Djokovic at the beginning of the season. Then along came Andy Murray this summer and produced a Big Four.
Having captured all but one of the Grand Slams and Masters Series events of this season so far, this quartet has already secured spots for the season-ending Masters Cup.
That leaves four places for the remainder of the field, and a large group of players are still in contention for those slots -- after all, the recent dominance of the Big Four means there's a relatively low bar for those aspiring to be the best of the rest.
Nikolay Davydenko is the only other player who can be penciled in as almost certain to qualify, meaning that the other three berths are entirely up for grabs during the five tournament weeks that remain before Shanghai:
The likes of Andy Roddick, James Blake and recent breakout Juan Martin del Potro will be in the hunt, while a potential powerhouse like Jo-Wilfried Tsonga must do a lot of catching up first.
The ATP Champions Race measures where the players stand in the pack – here's a look at their current positions, as well as a summary of their chances: