Surely, the former world no. 4 and 1987 Wimbledon champion didn't think Nadal would be on the throne of the rankings again. But unfortunately it was impossible for me to return to the court in the same condition as last night.
"For me it's not about London it's about longer term", Nadal said.
"I have to pull out".
Given the troubles he has faced in staying healthy in recent years, he is perhaps wise to prioritise the long term and skip the World Tour Finals as a precaution, with the hope it allows him to enjoy another strong season next year.More news: Supreme Court for special courts to deal with criminal cases against politicians
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"It's normal that at the end of the season after all the things that happened... The knee is always bothering a little bit but sometimes it's worse".
He further said, "I'm going to do my treatment, do my best to be playing in London, but I can not talk about that now because (it) is a day that is tough enough for me to pull out from here".
The Spaniard looked to be struggling at times yesterday during his three set win over Pablo Cuevas, and he confirmed it during his impromptu press conference that he called today.
Cuevas - undeterred by that break - produced a delightful "tweener" to win the opening point of the fifth game on Nadal's serve and, while he was unable follow up his scene-stealing trick shot by restoring parity, the 31-year-old won his next two service games to love as he settled into the match. "It's important to play tennis as long as possible".
"I'm going to enjoy today and then see how it goes tomorrow (Saturday)".