AMNA NAWAZ: Martina Navratilova was a high-profile force on the tennis court in the 1970s and '80s, with 59 Grand Slam titles, including 18 in singles, 31 in doubles, and 10 in mixed doubles.

She's remained a big presence in the tennis world, commentating and mentoring, and also using her platform to weigh in on issues off the court as well.

I caught up with her recently at the U.S.

Open in New York for our ongoing culture of sport coverage, part of our Canvas series.

In the tennis world, this is hallowed ground, Flushing Meadows, New York, the site of Martina Navratilova's very last match, a mixed doubles win at the 2006 U.S.

Open.

MARTINA NAVRATILOVA, Former Professional Tennis Player: Oh, Center Court is here at 10:00 at night.

I mean, I usually get very nervous before matches.

But that was excited and least nervous that I have been and played really well.

Most of the time, I was either one or two.

AMNA NAWAZ: These days, she's courtside behind a microphone watching today's tennis stars own the spotlight.

But a recent critically acclaimed Netflix documentary, "Chris & Martina," turned the spotlight back on her.

MARTINA NAVRATILOVA: Chris was the enemy.

But she's the one that I had to beat to get to number one.

AMNA NAWAZ: Capturing the intense rivalry between Martina and Chris Evert, whose win-loss record in singles is the best of any pro player, male or female, in history.

MAN: That was the first real rivalry that sparked that type of interest.

AMNA NAWAZ: It's a film about fierce competitors who also formed a deep and abiding friendship.

How did those two coexist over that time?

MARTINA NAVRATILOVA: You're only as good as your opponent.

You cannot hit great shots, you cannot be pushed to great heights unless you have the opponent that makes you have to do that.

So we made each other better.

And we -- I think we understood that, even though we didn't kind of appreciate it maybe that much during the -- I'm like, oh, my God, I got to play Chris again.

It's another 2.5-hour match, and it was always so physical playing her, because she doesn't miss.

So the contrast in styles was really obvious.

We appreciated each other always and respected each other.

AMNA NAWAZ: Navratilova was just 18 when she made the tough choice to defect from then-communist Czechoslovakia.

NARRATOR: She was playing temporary U.S.

residency.

AMNA NAWAZ: Alone in the U.S., she set her sights on beating then number one Chris Evert.

MAN: Yes.

MARTINA NAVRATILOVA: Chris was a lot more switched on to the emotional and mental state of the game.

I mean, I controlled my emotions at the end, but it took me a while.

And also I was alone.

I didn't have a coach.

I didn't have anybody to tell me, hey, listen, you're just beating yourself.

AMNA NAWAZ: There was also this narrative of sort of the American girlie-girl versus the tough communist player.

The media really fueled that.

I mean, did you feel that?

Were they trying to get you to say things about each other?

MARTINA NAVRATILOVA: Oh, they were writing one kind of story, and then, once I lived here, it was like, oh, look at all the jewelry she's wearing.

AMNA NAWAZ: About you making a home here in America.

MARTINA NAVRATILOVA: And I went from a communist to a capitalist with nothing in between, and I'm neither.

The press was definitely feeding off of the contrast.

AMNA NAWAZ: Yes.

MARTINA NAVRATILOVA: And it was hard because there literally was one guy that wrote good versus evil.

AMNA NAWAZ: Over 80 matches against each other, their bond grew and deepened as their careers came to a close.

MARTINA NAVRATILOVA: So, once she retired, all the walls came down, and then, once I retired, then we could really reminisce and be close.

But we always trusted each other.

There was always a trust that I had with Chris that never went away that I felt, if the push comes to show up, she's one of the people I can call, and she would be there for me.

AMNA NAWAZ: They faced their toughest battles yet together, early stage breast cancer and stage one throat cancer for Navratilova and ovarian cancer for Evert, a third round she announced in June.

MARTINA NAVRATILOVA: I'm all free.

AMNA NAWAZ: You're good?

You're in the clear?

MARTINA NAVRATILOVA: Free of everything.

I just have to do breast cancer screenings every six months, rather than once a year.

I'm on the lucky spectrum.

Chris had a more difficult cancer, but she's tough and she's going to be OK.

AMNA NAWAZ: How often do you two talk to each other?

MARTINA NAVRATILOVA: We stay in touch through text all the time, and we speak maybe once a week, once every two weeks.

So I will see her after the Open and make some more pesto for her, because she likes my pesto.

AMNA NAWAZ: That's what you make for is pesto?

MARTINA NAVRATILOVA: Yes.

AMNA NAWAZ: Martina, tennis is such a lonely sport, right?

You're out there alone.

You win and you lose, and you're alone.

MARTINA NAVRATILOVA: Right.

AMNA NAWAZ: And when you were going through your cancer battles, it was almost as if only the two of you could understand what each other was going through.

MARTINA NAVRATILOVA: You get used to that solitude and problem-solving on the court, and staying positive when things don't go right.

Otherwise, you would not be winning these matches at the end of the day.

And so this is just another match where it's not that much in your control, but the attitude and the -- getting the solution mindset was all -- is still there.

This is more life-and-death situation, but still you kind of get on with it and stay very, very positive, and that makes a big difference at the end.

AMNA NAWAZ: Navratilova herself made a difference for millions as a publicly gay sports star outed against her will in 1981.

There was a New York Times piece that said "Homosexuality is the most sensitive issue in the sports marketplace, more delicate than drugs, more controversial than violence."

I mean, that was the environment at the time.

MARTINA NAVRATILOVA: A hundred percent.

If a guy got caught shooting somebody, it was less of a problem than being gay.

Homosexuality was just a plague.

It was leprosy and cancer and all of that bad stuff put together.

Those people were not to be touched in any way or acknowledged.

So -- but, I mean, I was outed.

But I wanted to stay in the closet for the tour, not for myself.

I didn't care.

On the public space, it was a big no-no.

And it hurt me financially.

I didn't get any endorsements because of that, but I could still play tennis, and that was the biggest thing for me.

So I always encourage people to come out if they can, if they can still do their job and not get fired for it.

Please come out if you possibly can.

AMNA NAWAZ: But on the question of transgender athletes competing in women's sports, Navratilova has been firm in her opposition and faced heavy criticism for it.

You wrote an op-ed in 2019.

You said that trans women competing in female categories was the same as cheating, basically.

You said: "I'm happy to address a transgender woman in whatever form she prefers.

I would not be happy to compete against her.

It would not be fair."

That was a few years ago, so do you still feel the same today?

MARTINA NAVRATILOVA: If they undergo all this drug stuff, take hormones for a longer period of time... AMNA NAWAZ: Hormone treatment, transgender women.

MARTINA NAVRATILOVA: .. would they -- could we make it a fair fight?

Could they be included in a fair way in women's sport?

And then we talk, oh, maybe we handicap this, handicap that.

But on a team sport it cannot work.

Individual, you can -- but how do you measure that?

And at the end of the day, we realized there is no way to include males, however they identify, in female sports, because the bodies are just two different things.

And it cannot ever be a fair fight.

AMNA NAWAZ: I know you have spent so much of your career and your platform advocating for LGBTQ rights.

You have been an ally for so many people.

And, as you know, one of those groups came out, cut ties with you after these comments.

They said that your words are transphobic and they worried it would help fuel discrimination and violence against transgender people.

How do you feel about that?

MARTINA NAVRATILOVA: So, women's sex-based spaces need to stay on women, but everywhere else, trans, however they identify, cannot be fired for doing their job if they're doing their job.

You cannot be firing people because they're trans or identifies nonbinary or whatever.

So, all the rights to every job they have.

On female-sex-based spaces, which includes sports, that's a step too far, because then you are excluding women.

So you cannot be encroaching on our spaces at the expense of making them comfortable.

AMNA NAWAZ: This summer, tennis became the first major women's sports league to require genetic testing.

One advocacy group said that testing -- quote -- "invades all women's privacy, forcing them to give up their personal medical and genetic information."

Navratilova is undeterred by the backlash.

The ferocious competitor in her made it to number one, beat cancer, and is now watching a new generation claim its place in history.

Does a part of you still wish you were out there?

Like, do you have to keep yourself from running out on the court?

MARTINA NAVRATILOVA: If I could still play, I would.

At the same time, I'm so happy I don't have that stress.

So I'm good where I am, but I love to be a part of the sport that gave me my life.

And I'm happy to give something back.