EXCLUSIVE: Wild Serena Williams conspiracy theory gaining steam as Jim Courier throws support behind shock comeback

Serena Williams is 44 years old and hasn't played professional tennis in more than three years.

But speculation is heating up the popular pick for GOAT - greatest of all time - is planning a bombshell return to the court in the coming weeks or months.

The mother-of-two set tongues wagging earlier this month when an eagle-eyed reporter spotted her name in the Registered Testing Pool (RTP).

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The Whereabouts program, which Williams has rejoined, requires professional athletes to provide their location for one hour every day, to allow drug testers to randomly show up and test them during that period any day of the year.

While Williams herself has hosed down rumours of a comeback, fellow American legend Jim Courier is adamant there is only one reason she would re-enter the RTP.

"You have an app, it's called the Whereabouts program. So you give one hour a day when you have to be there," Courier explained to Wide World of Sports at the Australian Open in Melbourne.

"Most players do it at 6am or 7am in the morning when they know they're going to be either in their hotel room or in their house, wherever they are going to be in the world because it's literally 365 days a year.

"It's a huge hassle. The players all moan and groan about it... if you check out of a hotel, if you don't change that on your app and they show up at your door that counts as one missed test. And if you miss three tests during the course of 12 months, that's the same as failing a drug test so you are out for a while.

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"So no person that doesn't have intentions to play professional tennis is going to put themselves in that list, especially someone who has as much experience doing it as Serena Williams.

"Serena denied she's coming back, but I think unless she gets injured there is no doubt she's going to play somewhere at some point.

"Whether that's the mixed doubles at the US Open, whether that's doubles with her sister (Venus) somewhere, whether it's singles, only she knows. But there's no other way to interpret that."

Williams is regarded among the best tennis players of all time, and perhaps the most dominant ever.

She won 23 grand slam singles titles. Margaret Court and Novak Djokovic lay claim to 24 apiece.

Her last match was at the 2022 US Open, when she was beaten by Australia's Ajla Tomljanovic.

Tomljanovic was this week asked about a potential Williams comeback and said she would love to see it happen.

"I think it's great if she comes back. We definitely miss her," Tomljanovic said after her first-round win in Melbourne.

"I do hope in a way that I stay the last one (to play her) just because it's cool... I think we'll have to wait and see."

Courier, likewise, is keen to see if Williams can make a professional return.

Her older sister Venus continues to play professionally, and was given a wildcard to this year's Australian Open.

She won the first set against Olga Danilovic on Sunday before losing in three sets.

Courier didn't want to speculate whether Serena plans to play doubles with Venus, but is keen to see what unfolds.

"We can all speculate on what she's watching and why she's doing it, but the fact she's put herself back in that pool is good news for tennis fans," he said.

"She's global... So if she comes back to play it's going to get a lot of attention everywhere, not just in America.

"(Playing with Venus) would be great, we would love to see that. It would be amazing."

While age catches up to even the best athletes, Courier says Williams will know whether her body has what it takes to play tennis again.

"We saw the way that (Roger) Federer looked on the court the other night here at the opening ceremony (in Melbourne). You don't lose your racquet skills," he said.

"If you go back and practice a consistent amount from here, she will find the racquet skills.

"The challenge will be the movement. But if you've seen Serena lately she's been out promoting certain medications and she looks really fit.

"So she might have a chance of coming back and having good movement, which will be critical, obviously.

"We'll see, time will tell. But it would be shocking, frankly, if she doesn't play somewhere given the fact she's willingly put herself under this burden."

Williams' home slam, the US Open, begins in late August.