Knowing when it’s the right time to retire is one of the most difficult decisions a sportsperson has to make.

Go too soon and you’re left with that temptation to make a comeback. Stay on too long and you risk tarnishing the reputation you’ve spent years building as your fans and the general public only remember those tired and frustrating attempts to recapture former glories.

Rafael Nadal tennis

Roland Garros 2012 by y.caradec

For Rafael Nadal, he is reaching the point where he is going to have to make that decision.

The Spaniard’s current ranking of 10th in the world is his lowest for over a decade before he had won the first of his nine French Open titles.

For the first time in nearly as long, Nadal also didn’t start favourite in the betting to win at Roland Garros. The bookmakers were proved correct as Nadal lost to world number one Novak Djokovic in straight sets in the quarter-finals.

The way Djokovic’s dominance over Nadal grew as that match wore on offered clear evidence that the 14 times Grand Slam winner either hasn’t completely recovered from the injury and illness which ruined the second half of his 2014 or, worse still, he no longer possesses the ability to trouble the sport’s best players.

After playing Wimbledon last summer, Nadal featured in just three more tournaments last year as he was initially sidelined with a wrist injury before then having his appendix removed. Since his return, not only has Nadal struggled against the top players, but he has also been beaten by players he used to routinely swat aside like an irritating fly.

His quarter-final defeat by Tomas Berdych at the Australian Open ended a 17-match winning streak against the Czech. He then lost his first semi-final on clay for 12 years when he was beaten by Fabio Fognini in Rio de Janeiro.

Nadal was also shocked by Fognini in Barcelona. His other European clay court performances resulted in straight set defeats by Djokovic in Monte Carlo, by Andy Murray in the final in Madrid and by subsequent French Open champion Stanislas Wawrinka in Rome.

The 29-year-old has shown glimpses of the old warrior as he won titles in Buenos Aires on clay and in Stuttgart on grass, but he only beat one player ranked in the top 20 over those two tournaments. Following what should have been a morale-boosting win in Stuttgart, Nadal then lost in three sets to Alexandr Dolgopolov in his first match at Queen’s.

by  Carine06

Rafael Nadal during his quarter-final with Mardy Fish on Court 1, on Day 9 of Wimbledon 2011. by Carine06

His performances at Wimbledon probably shouldn’t be used as a guide as to whether he is in terminal decline given that the last three years have produced second round, first round and fourth round exits respectively.

How he performs in the American swing, in Asia and then back in Europe for the second half of the year will tell us whether Nadal can reach the same level of old. The one positive for him is that he doesn’t have many points to defend for the rest of the year, so his ranking shouldn’t drop much more.

But his ranking also means he has to play the best players earlier in a tournament. For a player who has won 66 singles titles in his career, Nadal will surely not accept being knocked out in the quarter-finals on a regular basis.