Serena Williams was not just Naomi Osaka’s idol as a girl but also the role model, along with sister Venus, that launched the Japanese star’s career.

Osaka’s father Leonard Francois had no background in tennis but, inspired by Richard Williams’ extraordinary success with his daughters, decided to try to repeat the story.

On Saturday, he will watch his younger daughter Naomi face Serena in a grand slam final and attempt to become the first Japanese player in history to win a slam singles title.

Naomi Osaka
Naomi Osaka will take part in her first grand slam final when she faces Serena Williams (Andres Kudacki/AP)

Naomi’s older sister Mari has struggled with injury and, at 22, is ranked 367, but is a key part of the story.

Osaka said: “She beat me 6-0 until I was 15, and then, I don’t know what happened, but one day I beat her 6-2.

“I do know for me one of the main things was that when I was practising with my dad, if my sister wasn’t there, I don’t think I would have made it. I think maybe both of us (her and Serena) have this really big sister connection.”

Not many players shout ‘I love you’ as a message to their forthcoming opponent in a grand slam final but then Osaka is not most players or most people.

Shy and slightly awkward off court, albeit with a natural comic touch, the 20-year-old showed steeliness and composure to defeat Madison Keys in her first slam semi-final, saving all 13 break points she faced.

Osaka’s development, especially her defensive abilities and court sense, has come under the tutelage of Sascha Bajin, who formerly worked as a hitting partner for Serena Williams and Caroline Wozniacki.

Bajin said: “She was a big hitter before I started with her. She knew how to play tennis. She maybe didn’t know quite how to handle it or control it, didn’t quite know when to pull the trigger, when not to.

“Maybe didn’t know that there were even other ways of putting pressure on the opponent. (Now) she’s more open-minded on the court about other things than just trying to crush the opponent.”

Serena Williams
Williamns took time out from tennis to concentrate on her daughter Olympia (Serena Williams/Instagram/PA)

Although Osaka is giving away 16 years of experience and 30 slam finals to her opponent, she goes in having won their only previous encounter in Miami earlier this year.

The caveat is that Williams was playing only her second tournament following the birth of daughter Olympia and was so disgusted by her performance that she walked off the court and left the grounds immediately.

Williams headed back home, did not play another tournament for two months and instead worked incredibly hard on her fitness. The results have been impressive and the 23-time grand slam singles champion barely broke sweat in dismissing Anastasija Sevastova in her semi-final.

Osaka said: “It’s really cool that I was able to play her so early. Of course, I feel like, since the circumstances were so different, I’ll be able to see how she changed and stuff.

Serena Williams
Williams will bid to equal Margaret Court’s all-time record for slam singles titles(Frank Franklin II/AP)

“When you just come back and then you make the finals of two slams, I think that’s really amazing. But I really feel like I don’t want to overthink this match, so I’m not going to think that she’s so much better than she was in Miami.

“I’m just going to go out there and play. Since I already know she’s a good player, I don’t want to be surprised if she plays better or not.”

Williams also feels the Miami clash will help her, saying: “It was good that I played her because I kind of know how she plays now. I was breast-feeding at the time, so it was a totally different situation. Hopefully I won’t play like that again. I can only go up from that match.”

The 36-year-old is back in the final in New York for the first time in four years and one step away, as she was at Wimbledon, from equalling Margaret Court’s all-time record for slam singles titles.

“I had an opportunity to do that this summer, and it didn’t happen, so I’m just going to keep trying,” said Williams. “If it doesn’t happen, I’ll keep trying for the next one.”