Former World No. 7 Mardy Fish had the pleasure — or misfortune — of playing both Novak Djokovic and Roger Federer at their best. Fish played against Federer a total of nine times, winning just once at the 2008 Indian Wells Masters, while he was winless against Djokovic in seven attempts.

With that experience, the American feels he has a good gauge of when the Djokovic-Federer duo were playing at their very best versions.

“The 2011 Djokovic and 2005 Federer were the best players that I've ever played,” Fish said on the Pat McAfee Show (via TennisWorldUSA).

But what if those two versions of two of the greatest tennis players of all time played each other?

According to Fish, Federer would beat Djokovic on a faster surface. But on a medium-paced or slower surface, the Serbian would win every time. In fact, Fish went on to declare the 2011 version of Djokovic as the best player of all time.

“If those two played on a medium-paced hard court, I think Novak would win,” Fish explained. “If they played on a faster surface I think Roger would win, and any slower surface Novak would win. 2011 Djokovic – the best player of all time.”

It's hard to argue with that.

In 2011, Djokovic was at the top of his game as he not only won the Australian Open, Wimbledon and the US Open — he also went 10-1 against Rafael Nadal and Federer combined.

Additionally, he went 70-6 overall during the year as well as ended the year as the World No. 1 with 10 titles won.

However, it's only at 36 years of age where Djokovic is now being more and more accepted as the tennis GOAT following his French Open win earlier this month that saw him break the record for most Grand Slam titles won with 23.

He could also do something that the 2011 version of Djokovic didn't and that's winning the calendar slam — winning every Grand Slam in a calendar year.

The closest the 23-time Grand Slam winner came to achieving the feat was in 2021 only to lose the US Open final.

However, with the Australian Open and French Open in the bag, Djokovic is in a very strong position to win the remaining two slams of the year and achieve a feat last accomplished by Rod Laver all the way back in 1969.