This tennis season has seen some incredible stories, most notable the comebacks of Roger Federer and Rafael Nadal. What must go hand-in-hand with those comebacks is the decline of the two players who kept Federer and Nadal away from winning Slams for the past few years. With both Novak Djokovic and Andy Murray dealing with injuries, their number of ranking points has declined tremendously. One year ago, the World #1 (at the time, Novak Djokovic) had over 16,000 ranking points. Right now, the #1 (Andy Murray) has 7,750.

This decline has allowed Roger Federer, playing an abbreviated season, to be close to retaking his World #1 ranking–something no man has held longer than him. Rafael Nadal, with his runners-up at the Australian Open and Miami and his dominance on clay, is even closer. These are the top two seeds in Montreal this week, and each has a real chance to become World #1 before the US Open even starts. With Andy Murray skipping Montreal due to injury, every point Federer and Nadal earn will just be gaining on Murray. The Brit has said that he hopes he is healthy enough to play the Masters 1000 event in Cincinnati next week–but if he doesn’t, he will automatically lose his top ranking.

How Roger Federer can become World #1

Federer has held the top spot more than any man, and his last stint at the top of the rankings was five years ago. Very few expected him to get back to having a chance at the top ranking, but then again, few expected him to be able to win two Slams in a single season ever again. Federer currently trails Andy Murray by 1,205 points. A title at a Masters 1000 event is worth 1,000 points (hence the name), while a runner-up nets 600. Federer cannot surpass Murray this week, though he can pull within 205 points with a title.

Federer has so far given no indication that he wants to skip Cincinnati next week, but I cannot (nor can most fans, I think) imagine Federer playing both Montreal and Cincinnati if he does well this week. He wants the match play to prepare for the US Open, much like he tried to get in one good run at a tournament before Wimbledon. If he does well in Montreal this week, he will probably withdraw from Cincinnati. If he loses early in Montreal (like in Stuttgart during his Wimbledon warmup), then he will want to play Cincinnati to get more matches in before the US Open.

Federer has said that he is not currently intent on taking back the World #1. Even if it is within reach, there is no reason for Federer to risk anything by playing too much this month. There will be plenty of chances to push himself to take World #1 after the US Open–there is no need to do anything about it now.

So, if Federer wins Montreal, his chance at World #1 relies on Nadal and Murray. He will pass Murray unless the Brit defends his runner-up showing at Cincinnati, but passing Nadal is more difficult. Unless the Spaniard loses early in both Montreal and Cincinnati (before the fourth round of both and before the third round of one), then Federer cannot take World #1 until after the US Open, unless he chooses to play Cincinnati as well. Nadal often struggles on these hard courts, but it’s hard to see him losing early both weeks.

How Rafael Nadal can become World #1

Nadal’s path is much easier, at least in the short run. In fact, not counting Cincinnati points, Nadal is currently ahead of World #1 Andy Murray. This means that if Murray cannot compete in Cincinnati–or loses early there–then Nadal will slide into the top ranking all on his own. In fact, Nadal can take the #1 ranking this week if he reaches the final in Montreal.

Even if Nadal cannot do it this week and Murray can defend enough points next week, there will be plenty of opportunities for the Spaniard to take the top spot. Nadal has very few points to defend after the US Open, so unless Murray can defend all or most of his 3,500 post-US Open points, Nadal will have a major opportunity to take the top ranking spot.

In fact, Nadal’s biggest competition might be Federer. The Spaniard has a 550-point lead on his Swiss rival in terms of points earned this year, but Federer does much better on the faster indoor courts towards the end of the season. Even if Nadal can take the #1 spot, holding off Federer from passing him afterwards could be difficult.

With both Djokovic and Stan Wawrinka–the two other players within close enough range to reasonable challenge for #1–having called an end to their 2017 seasons, the battle for #1 is really down to just Murray, Federer, and Nadal. In fact, it seems right now that the most likely outcome is that Nadal takes the #1 spot within the next two weeks–and then Federer takes it from him after the US Open or in the following months.