Five weeks remain in the ATP regular season, and four spots for the World Tour Finals  (year-end championships) have already been locked up. Rafael Nadal, Novak Djokovic, Andy Murray, and David Ferrer have all qualified for  that event in London already. After them, though, the race is heating up. Six players stand within 1,000  points of No. 5 Tomas Berdych. While Berdych and Juan Martin Del Potro are relatively safe, things are tight enough that just about anything still can happen.

Most of the top players will compete in four more tournaments this year, including this week. Two 500-level tournaments in Beijing and Tokyo fill this week’s schedule. Next week comes a Masters 1000 tournament in Shanghai. After a week with three 250-level tournaments with weaker player fields, two more simultaneous 500-level events follow in Basel and Valencia. Then the 2013 regular season ends with a final Masters 1000 in Paris.

In theory, a player could earn 3250 points in this span. Right now, that amount would be enough to jump a player all the way from nothing to No. 7 in the race for the World Tour Finals. Thus, if a lesser player can pull out an amazing month, he would have a chance at a miracle.

The likelihood of that situation is very low, though, and instead seven players stand within legitimate striking range of the No. 8 spot in London. If another top-15 player wins a tournament this week, or if any top-20 player can pull off a shocking run in Shanghai, they will join the conversation. Barring that event, there are only seven key players to follow.

As mentioned above, Tomas Berdych is probably safe at No. 5. If he collapses, there is a chance that others can catch him, but Berdych already has more points than the No. 8 player needed to reach London last year.

Juan Martin Del Potro at No. 6 in the Race to London also holds a fairly strong lead on the field, over 300 points ahead of the 7th position. While he has not officially qualified yet, Del Potro probably can lock up a spot with one more Masters semifinal, as can Berdych.

From Roger Federer onward, though, things get interesting. Federer stands at No. 7  in the Race but only 240 points ahead of No. 9 Richard Gasquet with Stanislas Wawrinka separating them.  Federer elected not to compete in a tournament this week. If Gasquet and Wawrinka meet in a Beijing semifinal, and Gasquet wins that match, Federer will be pushed back beyond the qualifying positions to No. 9 in the Race, or the first alternate in London. While Novak Djokovic’s presence in Beijing makes that semifinal unlikely, it is a possibility to bear in mind as the week unfolds.

Jo-Wilfried Tsonga has been hampered by injury in the second half of 2013, but he remains at No. 10 in the Race. Since Tsonga stands 340 points away from the No. 8 position, though, he will need a strong run in one of the remaining Masters 1000 events to qualify. If he does not reach a final at one of them, or semifinals at both, his chances will recede. The same goes for No. 11 Milos Raonic, who is in an even weaker position at 225 points behind Tsonga. Tsonga, unlike every other contender, does not plan to compete in either Basel or Valencia. However, if he is feeling healthy and puts himself in a competitive position with a good run in Shanghai, he might request a wildcard at one of those 500 tournaments.

In short, this is still very much anyone’s race for those final few positions. Also, it is possible that Andy Murray might withdraw from the World Tour Finals if his back surgery has not healed yet. If that happens, it opens up an extra spot for the seven players above to seek, making the final few weeks before London even more intense.