"For me it's about the longer term", said Nadal, after withdrawing from the Paris Masters. "It is a sad day for me".
While expressing disappointment over missing out on a Paris double following his French Open win earlier this year, Nadal revealed he will do his best to feature in the prestigious Tour Finals, but also said a decision would be taken keeping the future in mind.
"But his losses since then have only been [Juan Martin] Del Potro, Nadal twice and a tough one in Paris to [John] Isner where he held match points".
Nadal, 31, widely regarded as one of the greatest tennis players in history, has won 14 grand slams, two Olympic gold medals, and four Davis Cups with the Spanish national team. The knee is always bothering me a little bit but sometimes it's worse.
Rusedski is confident that Federer can make it 21 major titles in 2018; while Nadal has been backed to win the French Open at least a couple more times before he calls time on his career. "It's a tough situation but I tried my best. The way that I am today I do not see myself playing three more matches", he said.
The player didn't confirm his participation in the ATP Finals next week, a title that has eluded him so far.
He began the year with a five-set loss to Roger Federer in the Australian Open final.
Remarkably it is a tournament that the Spaniard has never won and he now faces an anxious week of rehab to make the field for the eight-man end-of-season finale.
"And I just think the level of tennis he is playing is a really high level with the exception of one or two points against Isner".