MELBOURNE, Australia -- Even for a sport that appeared to have been entering a transition stage for a while, this was a day to remember.
First Germany's Mischa Zverev, a journeyman, brought a tear to the eye of anyone who still yearns for old-time serve-and-volley tennis Sunday. He knocked top-ranked Andy Murray out of the Australian Open on a very warm Sunday evening in Melbourne.
Then Coco Vandeweghe, a straight-talking, big-hitting American who swaggers around every court like she owns the joint, walked out at Rod Laver Arena about four hours later and laughed and confessed that her bravado was just an act after she bounced top-ranked Angelique Kerber from the women's tournament 6-2, 6-3.
Vandeweghe and Zverev became the first duo to knock off two world No. 1s on the same day since Super Saturday at the 2003 US Open, when top-ranked Andre Agassi lost to Juan Carlos Ferrero in the semifinals and Justine Henin upset No. 1 Kim Clijsters in the women's final.
It seems the tectonic plates of the tennis landscape have been shifting for a while now. There's a little of the old here -- Serena and Venus Williams, Roger Federer and Rafael Nadal are all still alive -- but the chance for someone such as Milos Raonic or Jo-Wilfried Tsonga to rise up and finally break through and win a first Slam remains a possibility, too. No matter who wins the men's and women's titles now, Sunday's results reminded everyone of something Murray had been warned about before the tournament started.
Told that keeping the No. 1 ranking is harder than getting it in the first place, Murray deadpanned, "I hope not."
Murray knew all along that Novak Djokovic couldn't overtake him in the rankings here regardless of what happened, and he still lost despite the fact that Djokovic crashed out the tournament a round earlier. Kerber played like someone more fearful of failing than confident of more success. The harder she tried to hang on to No. 1 Sunday, the more it seemed to slip through her hands.
As for Vandeweghe, she could not tell a lie when complimented on her confidence.
"I guess I faked it a lot, because I felt like crap out there -- but fake it till you make it, I guess," Vandeweghe said jokingly after bashing 30 winners to Kerber's seven.
Serena Williams will now wrestle the No. 1 ranking back from Kerber if the American can win the title here, though this is the first tournament she has played since she lost the top spot to the German star at the US Open four months ago.
But Williams is playing for something even bigger: She's also trying to break a tie with Steffi Graf and win her 23rd Grand Slam singles crown, the most by any male or female player. With Kerber, who beat her in two of their past three Slam showdowns, gone, Williams' chances just got appreciably better.
Kerber has two career Slam titles, both of them won last year. She won the 2016 US Open to back up her Australian Open title and prove she was a deserving champ. Last fall, and again upon arrival here in Melbourne, she acknowledged she felt more pressure but was ready and eager for the challenge of being the top-ranked player in the world.
But then Kerber began her first defense of a Slam title here by admitting right away -- after she ran into a bit of trouble in her opener against Lesia Tsurenko -- that she had to beat back the memories of how she barely escaped match points early on before she won the 2016 title.
Kerber managed to get past the ghosts for two more rounds. But on Sunday, the 35th-ranked Vandeweghe started hitting rockets at her and never let Kerber back in the match. Kerber's best (some say only) weapon is her court coverage and fitness. But that wasn't good enough to save her on a day in which Vandeweghe's accuracy was sharp, and Kerber was more scattershot than usual.
"My game plan was to just execute, knowing she was going to get a lot of balls back," Vandeweghe said, "and just trust myself to beat her."
Afterward, Vandeweghe's jokes about not feeling amazing weren't quite as self-deprecating as Zverev's interview after he knocked off Murray. An emotional Zverev laughed and said, "I was just in a little coma, just serving and volleying my way through it. There were certain points -- I don't know how I pulled it off. I don't know yet how I feel, because everything is new to me, and everything feels unreal."
Afterward, Murray said Zverev deserved to win.
Vandeweghe -- saying she couldn't speak to whether Kerber seemed fragile or nervous -- said she thought she deserved to win, too.
"Last year, I came here and didn't even win a match," Vandeweghe reminded everyone.
But unlike the world No. 1s, she's in the quarterfinals now.