Dominic Thiem says Novak Djokovic is the best player mentally of all time, adding he had taken tennis to a new level.
In a question and answer section on his new website, Thiem placed both Roger Federer and Rafael Nadal in his top three sportsmen of all time, but he also had special praise for Djokovic.
"Novak Djokovic is probably the best player of all time mentally," Thiem said on his website. "We have had a couple of great fights.
"He is extremely professional, always focused one hundred percent. Novak took the issue of nutrition in tennis onto a higher level."
Thiem just made his own Grand Slam breakthrough, winning this year's US Open.
However, he admits he is unlikely to be able to mount a challenge to the big three for any of the history they are currently carving up between them.
"That is a huge challenge," he said. "I'm lacking about 15 to 20 Grand Slam titles."
Regarding women's tennis, Thiem said the GOAT debate came down to just two names.
"There are two names I consider the best of the best," he said. "Steffi Graf and Serena Williams - those two left their marks on the sport."
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