The only thing that could prevent Serena Williams from claiming more grand slam success is her own motivation, says Billie Jean King.

At last year's Australian Open, Williams surpassed Steffi Graf's previous Open-era record of 22 triumphs across tennis' four showpiece events – an achievement made all the more remarkable by the subsequent revelation that she did so while in the early stages of pregnancy.

The 36-year-old has missed each of the last four slams as she shoulders the responsibilities of motherhood and 12-time major champion King believes the American will go down as the greatest player in history.

"Serena can definitely win a slam as a mum," King told Perform.

"If she wants to she just has to go and pay the price of getting back on the court and doing the cross training that's necessary.

"But I think Serena will be the best player ever and I'm a big believer that every generation gets better and if Serena wants to do it, she will."

Williams' absence has opened the door for a number of the WTA Tour's perennial also-rans to announce themselves on the biggest stage, with Angelique Kerber the only quarter-finalist at this year's Australian Open with grand slam winning experience.

"The great thing about women's tennis is that it's wide open, anybody can win a tournament," added King. "There's no big favourites. I love it because every time I come to a tournament I'm like 'I have no idea' [who is going to win].

"Here's what happens with the media: they always complain when we don't have a great one like Martina [Navratilova] or Chris [Evert] or one of those like Evonne [Goolagong Cawley] or Margaret Court.

"But the point is then they always say 'there is no depth', and then you get what we have now is which is a really clear superstar out of this group and yet now they complain that there's no rivalry.

"The media's never happy either way but I love it the way it is.

"I take it for what it is, I've been through a lot of generations now and it's fascinating because I'm thinking 'who's going to win this when they go on the court' because I don't have a clue and I kind of like that."