, , and have dominated the sport for the better part of two decades and have 66 Grand Slam titles between them.

Djokovic alone holds almost every record in tennis, and the Big Three have won everything possible.

But Stan Wawrinka and have achieved one feat that the three multi-Grand Slam champions won't be able to match.

According to Ultimate Tennis Statistics, Wawrinka and McEnroe have had the "hardest" runs to a Grand Slam title. Swiss star Wawrinka has three Major trophies, the first coming at the 2014 Australian Open.

His run in Melbourne has been calculated as the most difficult path for a male singles champion according to the relative difficulty factor, which "represents how hard was to win the title compared to winning an average title of the same tournament level."

Wawrinka's maiden Grand Slam victory has a difficulty factor of 1.193, meaning it was 19.3 per cent harder to win than an average Major title.

At the 2014 Australian Open, Wawrinka was the No. 8 seed. He beat Andrey Golubev and Alejandro Falla, then got a walkover against Vasek Popisil before defeating four seeds in a row.

The Swiss ace defeated 17th seed Tommy Robredo in straight sets before upsetting No. 2 seed Djokovic 9-7 in a decisive fifth set.

Wawrinka took out seventh-ranked Tomas Berdych and, in the final, shocked world No. 1 Nadal to lift the trophy.

A former world No. 3, Wawrinka's 2015 French Open win was the second-hardest title with a difficulty factor of 1.186. Again, he beat four seeded players en route to the title, including Djokovic and Federer.

Meanwhile, McEnroe's 1980 US Open triumph has a difficulty factor of 1.184.

It was his second of seven Major titles, and the American beat Ivan Lendl, Jimmy Connors and Bjorn Borg on the bounce.

The difficult ratings are also calculated using the adjusted Elo rating system. Elo rankings consider factors like tournament level, the round in a match, the sets played, and a player's ranking at the time.

As for the Big Three, Djokovic's 2016 Aussie Open run is deemed the seventh hardest Major title, while Nadal's 2013 French Open victory comes in ninth place and Federer's 2012 Wimbledon win is in the 21st spot.