Serena Williams reacts as she plays Wang Qiang in their third-round singles match at the Australian Open in Melbourne, Australia, today. (AP photo)

MELBOURNE, Australia — Perhaps Serena Williams, now 38, will win a 24th Grand Slam title someday.

And maybe Coco Gauff, only 15, never will earn her first major championship.

Sure felt, though, as if a generational shift was being signaled today 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.

Gauff will be back at practice to prepare for a fourth-round match.

Serena Williams reacts as she plays Wang Qiang in their third round match at the Australian Open tennis championship in Melbourne, Australia, today. (AP photo)

That’s because the 67th-ranked Gauff took the latest step in her quick progression, becoming the youngest player in the pro era to eliminate a 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.