Rafael Nadal finished runner-up to Novak Djokovic at the ATP World Tour Finals in 2013. (AP)

Rafael Nadal’s participation in the Nitto ATP Finals is in doubt after he was forced to withdraw from the Paris Masters due to a knee injury.

The season-ending event, though, has always been a tricky one for the world No. 1, as he’s been forced to miss it six times out of 13 qualifications. He’s never won the tournament in his career, and has had a rollercoaster ride as far as his results go.

Here’s a look at some of his peaks and valleys through the years.

1

2006

A solid debut

In his first appearance at the Tennis Masters Cup in Shanghai, the number-two seed advanced to the semifinals, where he lost to Roger Federer in two close sets.

2

2009

An early exit

At the French Open that year, Nadal’s years-long winning streak at the tournament was snapped, and injury crimped many of his results in the season’s second half. He still qualified for the ATP World Tour Finals, but went 0-3 in the round-robin stage, losing to Novak Djokovic, Nikolay Davydenko and Robin Soderling, his French Open conqueror.

3

2006

A classic performance and a first final

For the first time in his career, Nadal reached the final of the tournament, losing to Federer in three sets. However, it was his semifinal win over Andy Murray in a third-set tiebreak that’s considered one of the decade’s best matches.

4

2011

A record-setting blowout

In the round-robin stage, Federer blitzed his longtime rival 6-3, 6-0. In the 26 matches they played against each other up to that point, this was the most lopsided result for either player.

5

2013

Turning the tables and another final

For the first time in his history at the tournament, Nadal went 3-0 through the round-robin stage. In the semifinals, he recorded his first-ever victory against Federer at the tournament, beating him in straight sets. Nadal went on to lose the final against Djokovic.

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