Some things in sport accelerate your heart rate. Like Conor McGregor snarling across a ring. Some make you nervous. Like Katie Ledecky in the next lane. Some make you sweat? Like LeBron James in your face. Some just make you consider prayer?

Like her.

Twenty-two Grand Slam titles. Ace collector. Forehand like the younger Ronda Rousey. Game face carved from stone. US Presidents are carved into Mount Rushmore, she hails from Mount Ruthless.

That face, what does it feel like seeing it from across the net?

"Intimidating."

Marion Bartoli, former Wimbledon champion and charming Fox Sports commentator, is grinning as she describes Serena Williams in her prime. A woman Bartoli likes, whom she has played four times, whom she has beaten, whom she admires. But before praise for Williams at her best, first a suggestion.

"To be honest," says Bartoli, "the only way to go on court and perform is to avoid the fact you're playing Serena and just not look at her. Otherwise you see someone inside the court constantly and just pounding balls at you, all the time so hard."

If you look up, says the Frenchwoman, you'll see a champion who dismantled Maria Sharapova in the 2007 Australian Open final 6-1, 6-2 in 63 minutes. "When you face that you feel like you have a bulldozer walking in your face."

Bartoli is fleetingly taking us where we'll never go but want to: Onto court and across the net from a woman who won her first Slam when Rafael Nadal was 13 and her last in 2016 when he was bravely scrapping to remain relevant.

To play Serena is to be granted access to her stage which is almost always a show court. Here ritual is reversed and royalty bow to her. But to others these cavernous courts can feel like public execution halls and the extra space on the sides and behind can play hell with perception. Lesser players need a few practice sessions here to acclimatise but Serena has the walk of someone who owns the title deeds to the place. Yes?

"Definitely," insists Bartoli.

And at her best what was her body language telling you?

"It was saying that I am going to hit 50 winners and you're not going to touch a ball."

Bartoli first played Serena in Miami, 2003, and says: "She saw me practising with my father and I think because we had this father-daughter relationship and it reminded her so much of her relationship (with her dad)... so (she and Venus) have always been so kind to me and my dad. They always came to me in the locker rooms, even asking about my results, how I was doing."

We do not see this genial Serena, we see only the one whose air of conviction transmits through our television. So when she's playing well, what does it feel like?

"The feeling is, it's not a tennis match," explains Bartoli. "Because normally a tennis match is about tactics, when you get into the rally, how you play the weakness of an opponent, maybe you get a short reply. Serena is taking that away, she doesn't want to get into this. It's all about the first shot (for her)."

It's all about applying force, pressure and her authority. "She's going to ace you because she throws the ball the exact same way and she can hit every spot. She's so precise. On the return if you're lucky she might not be sharp on the first or second service game... but if it's a semi-final or final, the first time you serve she will whack three winners."

Serena's record in the Grand Slams - 65 played, 33 times in the semi-finals or better - is something else because in the Grand Slams she becomes someone else. You can find proof in the corridors of the Australian Open, where her legend is inscribed on the walls: Champion in 2003, '05, '07, '09, '10, '15. "So many," people might whisper; "Not enough," she might smile.

"In Grand Slams it's different," insists Bartoli. "Dealing with two weeks and seven matches is completely different. You have to stay focused for so long, it's very draining mentally, it takes so much energy."

The press, the attention, the distraction, everything challenges the concentration. For players used to the less-complicated, one-week events it can be stressful; for Serena, it's the opposite, this is "her comfortable zone. She gets a day off, she can rest, she can treat her body".

But despite persuasive impersonations to the contrary, Serena is human and vulnerable. Bartoli outplayed her at Wimbledon 2011, partly by serving only first serves. "Even when I had second serves I was serving as hard as first serves. Just to take away the rhythm ... trying to make sure she didn't get into that groove of returning so well".

The key for Bartoli was holding her serve, but she sighs: "It's so difficult. Because she returns so well. You can think it's a great serve and she's just going to hit a winner."

It can be deflating which is why Bartoli's advice is simple: Get Serena into rallies. When she's swiping winners, the crowd is unengaged, like witnesses to an art exhibition. But, says Bartoli, much like Angelique Kerber did last year, "when you get into rallies, you will start to make her move, the points will be longer, the match will be longer, the crowd is going to get into it".

It only means you have to move faster, react faster, think faster. Do that for one match and you might be exhausted, but Serena's been rising, lifting, pushing for a lifetime.

"I don't think," says Bartoli, "people can even imagine how hard it is for her to keep on every single year raising the bar higher and higher and higher and keep her motivation with everything she's won." And been through. Which leads the Frenchwoman to declare emphatically: "The mental strength Serena has is the greatest of history."

In Melbourne, the American, a little edgy, a little frayed at the edges, will have to prove it again as she is challenged by a field whose improvement is a homage to her: She has forced them to become better. "She has more pressure," accepts Bartoli. "She knows when the girls are playing her they are going to bring their best game." Like Belinda Bencic will want to in the first round of the Australian Open.

But Serena will be where she wants. Big court, Grand Slam, chasing history. Ambitious, testy, anxious. Aceing, pounding, intimidating. Putting her talent on the line. One more match. One more year. One more game face.

•The Australian Open, the first tennis Grand Slam tournament of the year, will be broadcast live on Fox Sports and Fox Sports 2 (Singtel TV Ch114 & Ch115 and StarHub Ch208 & Ch209), Fox Sports Play app, and on foxsportsasia.com