For Rafael Nadal to return to is dominant form, he must follow the George Costanza adage, "It's not a lie if you believe it."

USA TODAY Sports reported that legendary women's tennis player Billie Jean King implored the former No. 1 men's player and dethroned French Open champion to change his train of thought to a more positive outlook to get back to his glorified past.

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"He's playing better than he was [before]," King said Wednesday. "I just don't know if he knows it.

"I would try to get (him) thinking differently. He keeps telling himself, 'I don't have.' I would keep trying to say what you do have."

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King's comments came as a response to Nadal's 7-5, 6-3, 6-1 quarterfinal loss to current No. 1 Novak Djokovic to end Rafa's five-year French Open reign (and string of nine Roland Garros titles in 10 years). To Nadal's credit, his comments have shown that he has fight left inside him.

"I was doubtful about myself the 11 years that I have been playing here," he said, according to ESPN.com's Peter Bodo. "I won nine and I lost twice. Doubts are good in life."

Bodo, however, added that Nadal's self-assessment seems hollow.

"Add those words to all the other puzzling, often unconvincing ones that this towering but clearly troubled champion has uttered over the course of the past six months," said Bodo. "It might seem unkind to pile on at a time when this latest wound is still so fresh, but this is an unusual moment, for Nadal appears to be in a downward spiral, the nature of which he doesn't recognize."

Thus, the need to heed the words of Costanza, Jerry Seinfeld's sidekick in his Seinfeld sitcom series. As King said, don't focus on the doubt, focus on the accomplishments.

"He is the first player I have actually heard at that level say he has absolutely no confidence," said Ilana Kloss, a former doubles champion and current commissioner of World TeamTennis, to USA TODAY.

The process won't be instantaneous, King adds.

"I would say you have to maintain this over a year, at least six months before it's going to kick in," King says. "So you have to be very patient."

The payoff would be well worth the wait, especially in spite of the naysayers.

Do you think Rafael Nadal's issues are more mental or physical at this stage of his tennis career? Comment below or tell us @SportsWN