Samantha Stosur has revealed the greatest regret of her celebrated tennis career - and it's not what most fans would think.

Stosur retired on Saturday night, blissfully content after fulfilling her childhood dream of winning a grand slam singles crown with a memorable triumph over Serena Williams at the 2011 US Open in New York.

The 38-year-old is also the only Australian woman since the legendary Evonne Goolagong Cawley more than half a century ago to claim major titles in singles, doubles and mixed doubles - all forms of the professional game.

Her place among the pantheons of Australian greats is secure.

For all her accomplishments, though, it's no secret that the one-time world No.4's biggest lament remains not winning a French Open singles crown.

It's just that losing the 2010 title match at Roland Garros to Francesca Schiavone, after saving match points against Williams in the quarter-finals and also taking out fellow world No.1s Justine Henin and Jelena Jankovic en route to the final, isn't Stosur's greatest disappointment in Paris.

Nor are losing semi-finals in 2009, 2012 and 2016.

No, Stosur's fourth-round defeat to eventual champion Jelena Ostapenko remains her most gut-wrenching regret.

Riding an eight-match clay-court winning streak, Stosur raced to a 4-0 lead inside 12 minutes against Ostapenko before disaster struck.

The then-title favourite suffered a stress fracture in her right racquet hand, lost the match and was never the same player again.

'The final is where you've got the real chance to win but Schiavone played too good that day and I wasn't able to produce the tennis that I did against Henin or Serena or Jankovic the round before,' Stosur recalled to AAP.

'That's the way it goes. But definitely playing Ostapenko when I fractured my hand and I didn't realise, when I was a set up, that was absolutely crushing.

'I didn't play for five months and I probably came back too early and even every year since then when I stepped on a clay court and started practising, I felt the same pain in my hand.

'So that one really hurt a lot and to go down in that way and with such an obscure injury, yeah, that was tough.'

Even if she'd somehow beaten Ostapenko, Stosur was 'no chance' of backing up for the quarter-finals.

'I couldn't even cut an avocado,' she said.

Yet she still has no idea how the injury occurred.

'I felt some pain in the knuckle a couple of days before in doubles, went to the doctor, got scans and they weren't even really sure,' Stosur said.

'But they said there was nothing in there that they could do and no one was really worried that I'd make it worse.

'But then when I went out and played, and as the match went on, I was in agony.

'I won the first set but I was in tears calling the trainer, I've never been so much pain.

'Then all of a sudden I was running around my forehand to hit backhands, which is something I never do.

'I ended up losing 6-4 in the third and it was a very painful match. Turns out that I had an injury that in a tennis player has rarely ever been seen. I still don't even know why.'