MICHEL MARTIN, HOST:

Let's turn for a few minutes to tennis where history is being made at the Australian Open. All four of the women and men that made it to the singles finals are in their 30s. That's an age that used to mean retirement was at hand if you were still playing at all, and the finals rekindled two historic rivalries. Early this morning, Venus and Serena Williams faced off in a Grand Slam final for the ninth time in their careers. It was 36-year-old Venus Williams' first major championship finals appearance since 2009, but it was the younger Williams sister Serena who took the victory and broke records.

At 35 years old, Serena became the oldest woman to win a Grand Slam singles title in the modern era. The win also marked her 23rd Grand Slam title, the most in the modern era. But there's nothing but love in this rivalry. In her championship acceptance speech, Serena made sure to thank her sister.

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SERENA WILLIAMS: She's my inspiration. She's the only reason I'm standing here today and the only reason that the Williams sisters exist, so thank you, Venus, for inspiring me.

(APPLAUSE)

MARTIN: Tomorrow morning, the men's final. That will bring Roger Federer, who is 35, and Rafael Nadal, who is 30, back together for the - get this - 35th time since 2004.

To talk about all this, we're joined now by Courtney Nguyen. She's a senior writer for WTA Insider. That's a website that covers women's tennis. She's with us now via Skype from Melbourne, Australia. Courtney Nguyen, thanks so much for joining us once again.

COURTNEY NGUYEN: Happy to do it.

MARTIN: So, first of all, were any of these four finalists expected to make it this far?

NGUYEN: Well, I think the only one that really was expected and was a pre-tournament favorite was Serena Williams. She was the number-two player in the world. Now she's the number-one player in the world by winning. But the other three, especially Venus Williams, really were unexpected storylines. Again, with Roger and Rafa turning back the clock - definitely not a final we expected on the men's side either.

MARTIN: Is this showing at the Australian Open Finals something unique - we're talking about age here - or are we seeing this elsewhere in professional tennis?

NGUYEN: Well, I think that the sport in general is aging, and it's the best thing about - that could happen to the sport. You cultivate these stars, and it's good business to kind of make sure that these stars stay in the game as long as possible. This is a trend that has been happening for a while, particularly spearheaded by Serena.

MARTIN: Is this about older players hanging on longer, being better able to preserve their bodies, you know, for whatever reason getting better training, better guidance about conditioning or is it - is there - are there a lack of younger stars coming up the ranks?

NGUYEN: I think a lot of it is the aspect of endurance. You know, tennis is a sport of teenage prodigies. It's what we've always been used to from the '70s and '80s. We haven't seen that very much in the 2000s, and I think the big reason why is because an 18 year old - it's tough for them to transition onto the pro tour and really be able to compete physically with the likes of, you know, these strong 30 year olds who get, as you said, the training and the conditioning.

MARTIN: As I mentioned you are in Melbourne covering all this, how are the fans taking all this in? Is this exciting? What are you hearing? What's the vibe?

NGUYEN: It's pure excitement. And I think that goes hand-in-hand with the nostalgia and the wistfulness of it all. I mean, these are four champions in Federer, Nadal and Serena and Venus who just have so much history down here in Australia, have so much history in the game. And this is a sport where we like to see our champions as much as we love to see that break-out ingenue start, you know, come through and make a name for themselves. These four names in particular are the ones that really tug at the heartstrings of tennis fans.

MARTIN: That was Courtney Nguyen. She's a senior writer at WTA Insider. She joined us via Skype from Melbourne where she is doing hard duty covering the Australian Open. Courtney, thanks so much for joining us.

NGUYEN: Always a pleasure.