Perhaps Serena Williams, now 38, will win a 24th Grand Slam title someday. And maybe Coco Gauff, still just 15, never will earn her first major championship.

Sure felt, though, as if a generational shift was being signaled Friday at the Australian Open, with a pair of monumentally significant third-round results hours apart in the same stadium: a surprising first-week loss by Williams, then a historic victory by Gauff.

First, Williams faltered down the stretch for her earliest exit at Melbourne Park in 14 years, a 6-4, 6-7 (2), 7-5 loss to 27th-seeded Wang Qiang of China. It pushed Williams' gap between Slam trophies to three years.

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"I'm way too old to play like this at this stage of my career," Williams said. "Definitely going to be training tomorrow, that's first and foremost - to make sure I don't do this again."

Gauff also was planning a practice session for Saturday, but hers was to prepare for a fourth-round match.

Coco Gauff of the U.S. celebrates after defeating Japan's Naomi Osaka in their third round singles match at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2020. Lee Jin-man / AP

That's because the 67th-ranked Gauff took the latest step in her quick progression, becoming the youngest player in the professional era to eliminate the defending women's champion at the Australian Open, beating former No. 1 Naomi Osaka 6-3, 6-4.

Only once the last point had been played did the preternaturally poised Gauff turn into a rather typical teen, joking about wanting to take "a selfie for Instagram" with Rod Laver, the 11-time major champion after whom the tournament's main stadium is named.

"Honestly, like, what is my life? Like, oh, my gosh!" Gauff told the crowd. "Two years ago, I lost first round in juniors and now I'm here. This is crazy."

It certainly is remarkable.

With a booming serve, a top-flight backhand and a winner's mentality, Gauff reversed the result from the first time she was across the net from Osaka, a former No. 1 who already owns two major titles at the age of 22.

When they played each other at the U.S. Open last September, Osaka won in two quick sets and then consoled Gauff, encouraging her to speak to the spectators who were pulling for her.

One reminder of just how young Gauff is: Most of the entrants in this year's junior Australian Open are older than she is.

Another: She is taking online classes and said she's been given permission to turn in homework late, "considering the circumstances."

Yet another: She doesn't have an official driver's license quite yet, stuck practicing behind the wheel with a learner's permit.

But put a tennis racket in her hands and move out of the way: Gauff is now 8-2 in her nascent Grand Slam career, with three of those wins coming against women who have multiple major titles. Her next match is against No. 14 Sofia Kenin, a 21-year-old American who beat Zhang Shuai of China 7-5, 7-6 (7).

Williams vs. Wang also was a rematch from Flushing Meadows last season - and the reverse result also happened for them. At the U.S. Open, Williams won 6-0, 6-1 in 44 minutes.

Wang credited that with prompting her to spend more time in the gym so she could add more oomph to her shots.

"I always believed I could do this one day," Wang said with a laugh. "I didn't know which day."