Maria Sharapova and Serena Williams have, what some would call, one of tennis' biggest rivalries, with the American taking a lead of 19-2 in their head-to-head, and it's clear that the two don't share a great friendship either.
The Russian has spoken openly about Serena Williams and what their friendship and rivalry means to her and her career, even mentioning Williams in her book 'Unstoppable: My Life So Far', describing her as 'intimidating'.
The five-time Grand Slam winner said: "This is very special. I think we have a professional relationship. It would have been strange if in the book I didn't speak about one of my greatest rivals."
The Russian also commented on her respect for the American.
"Over the years, many things were said about our relationship and rivalry. We should be celebrated for what we achieved.
"We have very different backgrounds, but both of us found a way to get to the top. I have much respect for what she did and her ability to keep fighting to have successes."
However, despite the pair having what appears to be a professional relationship, when asked if they could be friends once their respective careers have come to an end, Sharapova didn't think that would be the case.
She replied: "I don't think so. I was lucky to make a lot of friends at a young age in my career who are very important for me.
"At the end of the day, we will always be opponents. Since a young age, when we had never played against each other, I was feeling this competitiveness. I wanted to get to that level and show that I can beat her."
This follows Sharapova praising Roger Federer for his 'off-court life'.
She said: "I think he is an inspiration in many aspects.
"Not only for me, but for many players. But I think there is a difference between men and women. For women there are other expectations in life and you want to do other things like starting family.
"He has always been an inspiration for me."
Sharapova is set to face world no.7 Caroline Garcia in the first round of the Stuttgart Open on Monday, where she'll be looking to to take her head-to-head lead of meetings to 5-0 against the French five-time WTA singles winner.