There are still a few matches to play in the ATP season, but Rafael Nadal has already locked up the year-end number one spot in the ATP World Rankings.

With the Spaniard’s win over Stanislas Wawrinka in the group stage of the ATP World Tour Finals, Nadal not only earned a semis slot in the final tournament of the ATP 2013 season but also clinched the title as tennis’s best in 2013.

This is actually the third time in his career that the 27-year-old has ended up in the top spot in the end of year rankings. He achieved the feat in 2008 and 2010.

The third time could be the charm and the sweetest too: Nadal was coming off a career-threatening knee injury in 2012, and his road back to recovery apparently was the same road back to the top of the tennis world.

Nadal finished with just 42-6 win-loss record in 2012 and the most disappointing loss was in the Round of 64 upset to Lukas Rosol at Wimbledon. By end of 2012, he dropped all the way to 5th place in the ATP World Rankings, his lowest placing since climbing to the Top 10 in 2005.

After a seven-month lay-off, the Spaniard slowly but surely got back to his old form— winning tournaments left and right and accumulating all-important ATP points since February 2013.

But it was not without struggle. Nadal showed some rustiness post-surgery and got another Wimby beating at the hands of another unheralded player in Steve Darcis, who beat Nadal in the opening round in the 2013 Wimbledon Championships.

From that point on, however, he became a man on a mission to prove that the first round upset was a fluke and that he belongs with the elite players in the world.

He won three tournaments in August and eventually grabbed the No. 1 spot back from rival Novak Djokovic in the latter part of the ATP season.

The overall result was an impressive 10-championship haul in 2013; two Grand Slam titles (U.S. Open and Roland Garros), five ATP World Tour Masters 1000 titles (Cincinnati, Canada, Rome, Madrid and Indian Wells) and three titles more (Barcelona, Acapulco and Sao Paolo).

"Today, it was more important secure the No. 1 at the end of the season," said Nadal. "[It is] one of the best things that I have done in my career – coming back to the No. 1 after three seasons. That's very difficult in our sport … and the good thing is [that] after two matches now, I can really be focused only on the tournament because the year end is over," said Nadal to the official ATP website after clinching the most prized possession in the sport.

That sounds like a final warning from the World No. 1 when the London tournament in London enters the knockout stages on Saturday.