MELBOURNE, Australia -- Once again, Serena Williams came within reach of a record-tying 24th Grand Slam singles title, playing well enough Thursday to get to the closing days of a major tournament. And once again, Williams couldn't quite get it done, as she was defeated 6-3, 6-4 by Naomi Osaka in the Australian Open semifinals.

Osaka, who also beat Williams in the chaotic 2018 US Open final, reached her fourth major title match and stretched her winning streak to 20 matches by claiming the last eight points.

"I don't know if there's any little kids out here today, but I was a little kid watching her play," Osaka, 23, said about Williams, 39, "and just to be on the court playing against her, for me, is a dream."

Osaka will face 22nd-seeded American Jennifer Brady for the championship Saturday. Brady beat No. 25 Karolina Muchova 6-4, 3-6, 6-4 in the other semifinal.

Brady claimed an epic, 18-point last game to reach her first Grand Slam final. She dropped to her back at the baseline after saving a trio of break points, then converting her fifth match point when Muchova sent a forehand long.

"My legs are shaking," Brady said. "My heart is racing."

She lost to Osaka in a three-set thriller in the US Open semifinals last September.

"Everyone's just really excited whenever they play their first final," Osaka noted about what awaits Brady, "but they're also really nervous."

The No. 3-seeded Osaka's Grand Slam collection includes last year's US Open and the 2019 Australian Open, and she is without a doubt the most dangerous hard-court player in the women's game today.

That used to be Williams, of course. But she was off target too much in this contest, finishing with twice as many unforced errors (24) as winners (12).

"I could have won. I could have been up 5-love," said Williams, who instead took a 2-0 lead at the outset before dropping the next five games. "I just made so many errors."

Her forehand, in particular, went awry, with no fewer than 10 unforced errors off that side in the first set alone.

"Too many mistakes there," she said. "Easy mistakes."

Williams' frustration was visible early in the second set, when she leaned over and screamed, "Make a shot! Make a shot!"

After collecting her professional era-record 23rd Slam singles trophy at Melbourne Park while pregnant in 2017, Williams reached four major finals and lost them all.

She also now has lost in major semifinals twice in that span.

The 23-year-old Osaka joined two other players to win each of their first two major meetings against Williams. Williams' sister Venus won their first three major meetings at the 1998 Australian Open, 2000 Wimbledon and 2001 US Open. The other is Jennifer Capriati at the 2001 French Open and 2001 Wimbledon, according to ESPN Stats & Information research.

Spectators were back in the stands at Rod Laver Arena on Thursday after they were barred from attending the tournament for five days during a local COVID-19 lockdown. About 7,000 people were allowed into the stadium for Williams-Osaka, roughly half of capacity.

Ushers walked through the aisles at changeovers to remind fans about wearing masks.

On the hottest day of the hard-court tournament so far -- 85 degrees Fahrenheit (30 Celsius) -- Osaka got out to a shaky start, perhaps prodded into pressing in her opening service game by a booming cross-court backhand return winner from Williams on the match's second point.

That was followed by a double fault, a wild forehand and, eventually, a netted backhand that handed over a break. Quickly, Williams went up 2-0, then held another break point with a chance to lead 3-0 after another double fault by Osaka.

"I was just really, like, nervous and scared, I think, at the beginning," said Osaka. "And then I sort of eased my way into it."

Didn't take long to right herself.

Suddenly, it was Osaka powering in aces, putting groundstrokes right where she wanted, covering the court so well. Williams' movement has been terrific in Melbourne, but she was flat-footed this time.

Osaka never has tried to hide how much she admires Williams and models her game after the American's.

Both are predicated on the same basic elements of big serves and quick-strike forehands, and not only did Osaka do both better on this day, she even sounded just like her idol, screaming "Come on!'' after several key shots.

There was one last test for Osaka. A trio of double-faults in one game -- she wound up with eight for the match -- allowed Williams to break for 4-all.

But Williams would not win another point.

Osaka regained her composure immediately, breaking back at love with the help of a pair of backhand winners and a double-fault from Williams, then holding at love to end it.

The Associated Press contributed to this report.