What's going on with Nadal and the end of his season?

Where in the world is Rafael Nadal? The world No. 1 hasn't competed since retiring from the US Open semifinals on September 7. Though he's expected to return to the tour in Paris next week for the final ATP Masters 1000 of the year, the experts aren't so sure it's a good idea.

Nadal has had trouble playing on hard courts thanks to recurring knee injuries. This year, it was an injury to his right leg that forced him out of the Australian Open quarterfinals against Marin Cilic, and right knee pain saw him stop after two sets against Juan Martin del Potro in New York. Despite being the top seed at the ATP Finals last year, Nadal withdrew after one match with a right knee injury.

Quite possibly, Nadal will start doing what Roger Federer does in skipping the clay season, and adjust his hard-court season to suit his body. The issue is that nearly half of the season is played on hard courts. Of the 68 tournaments on the 2018 ATP calendar, 33 are on outdoor and indoor hard courts. A closer look shows that from the Rogers Cup in early August until February, every single tournament is on hard.

In recent years, Nadal has already been adjusting his schedule, though not dramatically. Of Nadal's five titles this season, just one has come on hard courts (Toronto), and of his nine ATP events played in 2018, just three have been on hard.

All that's left for the King of Clay to focus on this season is Paris and the ATP Finals in London. London is of particular interest because, somehow, the 17-time Grand Slam champion has never won a year-end championship.

The Spaniard is also at risk of losing his year-end No. 1 ranking to Novak Djokovic. The Serbian is just 215 points behind Nadal, and plans to play both Paris and London.

According to Paris tournament director Guy Forget, Nadal has been practicing privately in Majorca, but "training does not mean always being ready to compete at a high level." Forget has not spoken to Nadal directly but instead got in contact with his agents.

At 32, how important is it to Nadal to clinch the year-end No. 1 honor and add an ATP Finals crown? The world will soon find out.

Follow Nina on Twitter @ninapantic1.

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