On his 25th birthday, a mature Marat Safin outlasted the world's No. 1 player, Roger Federer, in five sets in the Aussie semis. Sean Garnsworthy/Getty Images

Following Marat Safin's epic five-set upset of Roger Federer, and Serena Williams' gutsy three-set win over Maria Sharapova at the Australian Open, SI.com spoke with Sports Illustrated senior writer Jon Wertheim from Melbourne, Australia.

SI.com: What was your take on today?

Wertheim: Where to begin? This was the Australian Open's answer to the U.S. Open's Super Saturday. In the first match, Serena showed a tremendous amount of courage beating Sharapova, a player who had beaten her in their past two matches and was not the least bit intimidated by Serena's aura. Sharapova had match points against Serena, but this wasn't a choke. Serena simply didn't miss on the biggest points. After the match she celebrated more than I can ever recall. This was a real "statement match" for her, both with respect to Sharapova -- probably her biggest rival, and the player who has eclipsed her as the face of the Tour -- and with respect to letting everyone else know, "I'm back."

Lindsay Davenport followed with what was an ugly win over France's Nathalie Dechy. This will not go down as one of Davenport's better matches -- she deserved to lose and probably would have done so against a player better able to handle the big stage. But credit her for grinding out a match for the second time in two days and reaching her first Grand Slam final since the 2000 U.S. Open.

The night match was weird and wonderful, with Safin ousting the king, Federer -- albeit on his seventh match point -- in a match that ended well after midnight. This was an insta-classic. Terrific tennis. Terrific drama. Terrific win for Safin. We were waiting for one player to stand up to Federer and mount a real challenge, and we found him.

SI.com: Is this the Safin we've been waiting to see?

Wertheim: Yeah, this was the good Safin (heavy baseline game, powerful serve, pinpoint returns and incredible shotmaking) without the bad Safin (the mental lapses and collapses under pressure). We've known for years that this guy is loaded with talent but too often he's combusted.

Safin turned 25 today and -- though it's obviously an artificial mark -- you get the sense he's matured. He didn't lose his head against Federer, even when he was down a set and 5-2 in the tiebreaker. Afterward, he was philosophical and serious, trying to relish a huge win while remaining calm, because he knows he still has to play the final.

SI.com: Who are you picking as his opponent?

Wertheim: It will be interesting because Lleyton Hewitt is probably the favorite on paper, but Andy Roddick ought to be the fresher player. Hewitt has the crowd behind him -- though not as much as you might think -- and has more or less owned Roddick of late. But Roddick has cruised through the draw and hasn't faced a top-20 opponent, while Hewitt has worked overtime. Last night's match against David Nalbandian was great theater, but it had to take something out of him.

I also wonder how Hewitt's sportsmanship -- or lack thereof -- will affect Roddick. Players have come to expect a certain level of pugnacious, distasteful behavior from Hewitt, but it's clearly affected his last four opponents. How will Roddick, a guy with a temper and a disdain for bush-league behavior, handle it when Hewitt pumps his fist or yells "C'mon" after a double fault?

SI.com: Any other thoughts?

Wertheim: We had another chapter in the Serena-Sharapova rivalry -- the future of the women's game. We had Davenport validating her decision not to retire. We had Safin upsetting a player who many are claiming is the best ever. We had the two defending Wimbledon champs holding match points and losing. Great tennis, exciting matches -- a banner day for the event and the sport.