Nadal had been beaten 6-2, 6-4 by Alexander Zverev in his opening group stage match at the Tour Finals, a tournament he has never won.
The Spaniard has rarely even made it to the year-end championship due to injury and once again came to London under an injury could after pulling out of the Paris Masters at the semi-final stage.
He refused to blame the underlying injury for the defeat in his post-match press conference before being asked by Italian tennis reporter Ubaldo Scanagatta whether "concentration on tennis life has been a bit different" since he married long-term girlfriend Mery Perello last month.
“Honestly, are you asking me this?" Nadal said.
"Is a serious question or is a joke? Is it serious?”
Scanagatta replied that it was serious and tried to clarify but was then interrupted by Nadal.
"I am surprised. Is a big surprise for me you ask me this after I have been with the same girl for 15 years and having a very stable and normal life," Nadal added.
"Doesn’t matter if you put a ring on your finger or not. In my personal way, I am a very normal guy."
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Nadal then asked the journalist about his own marriage before terminating the English segment of the press conference.
"We move to Spanish, because that’s bulls***," Nadal said.
"Thank you very much.”
Scanagatta has since said that he hopes Nadal apologises because "it was a normal question".