The sixth-seeded Australian reached the French Open semi-finals for the third time in four years by outfoxing 15th seed Dominika Cibulkova 6-4 6-1 on Tuesday, leaving the Slovak clueless on how to adapt to a style that is more often seen in the men's draw.
"Her topspin and her serve... She played like a man, and it's really hard to play against a man," Cibulkova told a news conference.
"It was driving me crazy on the court today. So it was really, really hard. Really tough."
It is not the first time such an observation has been made at Roland Garros, where Stosur reached the last four in 2009 and the final in 2010.
Two years ago, after Serbian Jelena Jankovic was thrashed 6-1 6-2 in the semi-finals by Stosur, she said: "To be honest, she kind of has almost a game like a man.
"That's what it feels like. When I look at how the men play, she has a very good kick, which not many women have. It's very heavy, the spin. And then she runs around the forehand."
"From 10, 11, 12 years old I worked on it. As you get older and you get stronger and get bigger it becomes more and more effective," Stosur, who has not dropped a set at Roland Garros this year, explained.
"So I think that probably was ingrained in me probably from a young age. At that age, who knows if you're ever going to make it to this point? I guess that's just good looking ahead from the coach I had at that time.
"Then the spin and all that, just kind of growing with my game and working with (coach) David (Taylor) really improved that in the last four or five years that we've been together."
It was not just technique, but also composure that helped Stosur tame the hard-hitting Cibulkova on Court Philippe Chatrier as she staved off nine of 10 break points.
She struggled at first with her opponent's power but Cibulkova collapsed after losing the opening set, with Stosur winning six games in succession to wrap it up after 85 minutes.
Stosur will start as favourite against 21st seed Errani, who had never beaten a top 10 player in 28 attempts before knocking out world number 10 Kerber.
But Stosur was reluctant to forecast the outcome, telling a courtside interviewer: "It can be a great day or a bad day."
A dejected Cibulkova conceded there was not much she could do.
She told a news conference: "She's putting the ball so high. Her kick-serve gets me out of the court so much that I cannot do anything. So if I want to go against the serve I go here, and if I want to go back I'm like three metres behind the baseline."
Stosur broke twice in the opening set and stamped her authority on the contest when she saw off two break points in a hard-fought seventh game.
She used her kick-serve to pull her opponent off the court, opening it up for a forehand winner as she claimed the first set after 54 minutes.
The same trick worked again in the second game of the second set, with Stosur saving another three break points en route to a straightforward victory.