Roger Federer and Rafael Nadal
Roger Federer and Rafael Nadal have a combined 36 Grand Slams. Pictured, Nadal of Spain reacts during the award ceremony after losing his Men's singles final match against Roger Federer of Switzerland on day eight of 2017 ATP Shanghai Rolex Masters at Qizhong Stadium in Shanghai, China, Oct. 15, 2017. Lintao Zhang/Getty Images

Maria Sharapova believes it is unfair to compare the legacies and success of Rafael Nadal and Roger Federer purely through numbers.

Nadal is currently playing at the French Open where he is a heavy favorite to extend his record to an 11th title as he defeated Richard Gasquet on Saturday to reach the last 16.

A win in Paris would take the Spaniard's tally to 17 Grand Slams, three behind rival Roger Federer who many in the tennis world believe is the sport's greatest of all time (GOAT).

Nadal also trails Federer in overall titles with 78 compared to the Swiss legend's 97. However, he leads in their head-to-head meetings with 23 wins in 38 encounters.

In addition, the 31-year-old is the only player to win a single Grand Slam 10 times while his 50 consecutive sets won on clay is an all-time record on any surface.

It is one of the reasons why the duo should not be compared, according to Sharapova, who recently made headlines last month for posting a tweet labeling Nadal as the GOAT after they both trained together.

"I don't know if, when you're that successful, if it's even fair to measure them in numbers, because you don't want to take anything away from somebody else that's achieved maybe just as much or maybe even more or a little bit less," Sharapova said, as per Express. "I think it's pretty remarkable what he's [Nadal] done in his career. I think when you get to a certain point, you know, those numbers, I mean, there are a lot of people that can be considered greatest of all time, right?"

Sharapova went on to heap praise on Nadal, as she revealed her admiration for his spirit and work ethic despite age and recurring injury problems.

"Yeah, I have a lot of admiration for him. I have always — I have loved the spirit that he carries on with, you know, the focus," she explained. "You know, it goes back to kind of the fire question. I think he only knows how to go at 100 percent."

"If you look at the practice schedule he's out there for - he won two events, and in Rome, he's practicing for three hours a day, he knows that that's what works for him and he's going to deliver that no matter his age, no matter the injuries, he shows up. ... That's incredibly admirable, because the older you get in this sport, the more physical it is, tougher it is on the body. We know that. So, yeah, of course I admire not just him but there are many players that I admire on that level."

Meanwhile, Sharapova is set to renew an old rivalry with Serena Williams as they meet each other Monday in the fourth round of the French Open.

Coincidentally, Federer recently called Williams one of the GOATs in tennis, adding he believed the American had a case even with both genders included in the conversation.