The Final Countdown

We're getting down to the wire at this year's ATP Championships in London, with just a few more round robins left before the final four are determined. And while we might not have yet seen a lot of drama on court this week -- only one match so far has gone three sets -- as the very best in tennis try to keep their seasons going a little longer, almost everyone still has a chance to make it to championship weekend. And that just might mean the most excitement is still to come.

World #1 Novak Djokovic is looking for a three-peat at the O2 and hasn't lost a set since the Shanghai semis. This week he's dropped just five games, seven fewer than his nearest competitor, and has notched wins over the other two players who've won Grand Slams this year. With a 16-2 record against his last remaining opponent Tomas Berdych, it seems inevitable he'll make it out of his group. The Czech, meanwhile, will likely vie with Stan Wawrinka, who made the semis here last year. Berdych lost to the Swiss #2 pretty handily on Monday, but managed a one-sided win over post-season newbie Marin Cilic just yesterday, when Nole got some definitive revenge over his Australian Open vanquisher. Things could get interesting tomorrow when the foursome take the court -- Cilic doesn't have a great record against Wawrinka, but the big man has struggled in recent weeks and might be a little vulnerable this time around. And while Cilic is disappointingly 0-2 in his London debut so far, he has certainly shown he has the ability to shake things up.

Meanwhile standings in the second set of World Tour Final qualifiers all come down to tonight's headline show. Six-time champion Roger Federer, perfect so far this week, will take on Andy Murray, who's been making quite a push in the latter parts of the season. The two are dead even at eleven wins apiece in their head-to-head, and with so much on the line now, they'll each be bringing their A-games to tonight's battle. Waiting patiently in the wings will be Kei Nishikori, the only London first-timer still in contention for a final spot -- earlier today he squeaked past David Ferrer, Milos Raonic's replacement, in the only three-setter played this week. With his own straight set win over Murray in the round robins, the U.S. Open runner-up still stands a chance of reaching the semis if Roger falters tonight.

Time is quickly ticking down at this year's World Tour Finals, and pressure is high across the field -- while things look good for a championship showdown between the top-two, most decorated players out there, there's plenty of room for others to spoil the favorites' fun. And if we've learned anything this tennis season, it's that no one is safe for long.