For a great champion, Serena Williams sometimes teeters on the edge of meltdown. However a 6-3, 6-0 blitz of the estimable Latvian Anastasija Sevastova here on Thursday night went a long way to re-establishing the aura that has already put the American one clear of Steffi Graf’s 22 grand-slam titles and one short of the all-time record set by Margaret Court.



When her confidence is fully restored – and that could happen against the star of this 50th US Open, 20-year-old Naomi Osaka, in the final on Saturday – two years of uncertainty in the women’s game will be over.



Since Williams won the Australian Open last year before leaving the tour to have a baby, there has been a different women’s champion at every major. If she wins her seventh title from nine finals here, all things are possible.



Osaka, the Japanese prodigy who spent much of her childhood in New York, booked her place in the final when she took last year’s runner-up, Madison Keys, to the cleaners. She won 6-2, 6-4 in the second semi-final, by which time the heat outside the closed roof of the Arthur Ashe Stadium had been quelled by a brief shower.

Keys, who can falter on the big stage, looked on the point of collapse a few times but mustered her resources in a combative rearguard action. But she could not crack Osaka’s defence.



What an occasion it will be for Osaka, who said later of her staggering resolve in saving all 13 break points against her, “This is going to sound really bad, but I was just thinking, I really want to play Serena.” She is the first Japanese woman to make a grand slam final.

Williams said in the aftermath of what turned into a cakewalk, “A year ago I was fighting for my life after I had the baby. I’m so grateful for the opportunity to play on this court. Whatever happens, I have already won. And I’m just beginning. It’s only been a few months. I’m really looking forward to the rest of the year and next year. I’m really excited about that.”



On the available evidence – and a vast history – she is not going anywhere but up - at nearly 37. Osaka will need to be at her best to compete.



“I got to play a little better,” Williams said courtside, reaching for understatement. “The crowd was so intense and helped me out after those first two games. I want to give them the best that I can.”



As for her strategy of attacking the net, she said, “I’ve been working hard on my volleys. I have won a few doubles championships. So I know how to volley, but I usually come [to the net] just to shake hands. I wanted to try something different today and it worked in my favour.”

Naomi Osaka is into her first grand slam final. Photograph: Sarah Stier/Getty Images

But, in a shaky beginning, that old self-doubt lingered long enough for Sevastova to break and hold, shocking the gathering into mute disbelief.



Williams was charging the net as if in a hurry for a dinner date, but took a while to be certain in the volley. By the end, she had won 24 points from 28 visits to the net. Once her minor crisis had passed, her awesome serve started clicking like a machine gun.



Amazon Prime, who have had a mixed debut as the game’s UK broadcaster,

did produce a stunning statistic: Williams was averaging 107mph on serve – just one mile an hour slower than Kei Nishikori – with a maximum of 118mph. And her go-to weapon steadily forced Sevastova deeper and wider.



The Latvian’s reliance on placement over speed was exposed when Williams broke back in the fourth game, and again for 4-2. Forced to go for the lines, Sevastova’s solid groundstrokes, the foundation of her game, began to crumble.



It had taken Williams half an hour to settle into that familiar, chilling rhythm and, once she took the sting out of her opponent’s slice, especially on the backhand, she looked more like the player who had taken just 91 games, one surrendered set and six-and-a-half hours to account for five players in this tournament. Only Kai Kanepi has taken a set off her.



After 40 minutes, Williams bullied her way artfully to take the first set, reading Sevastova’s grip switch for the slice with uncanny accuracy, which allowed her to grab time for a dash to the net.



It was odd to note that Sevastova, at 18 in the world, is ranked eight places above Williams, but the American – like her friend Tiger Woods – is climbing back to her best. And, when Sevastova dropped her serve at the start of the second set, she knew she was looking across the net at the best player in the world, whom the tournament recognised with a No17 seeding for the fortnight.

That victory became undeniable as Williams rushed through the second set in 27 minutes, bagelling her dazzled foe, who at times was nearly knocked off balance by the power in the champion’s shot.