There is a fairytale quality to the idea that the Cinderella Errani could gatecrash Queen Maria's Roland Garros ball, while all the indicators suggest the script is written for Sharapova to become the 10th woman to complete the career grand slam.
It would be fitting, after claiming the other three titles before being cut down by a shoulder injury that needed surgery in 2008, that she should rise again to the pinnacle of the sport to win the only title missing from her collection of majors.
The second seed has already reclaimed the number one ranking by beating Petra Kvitova in the semis, the latest imperious performance in a march to the final that has seen her drop just one set.
"Errani, as amazingly and bravely as she'd played, I just don't see how it can be enough for Maria's return of serve," explained 18-times grand slam singles champion Navratilova.
"(The return) is her best shot, and Errani's serve is her worst shot.
"So that's a really bad matchup. When you talk about somebody that has a better chance of breaking their opponent's serve than holding their own, in my eyes, then it's not looking so good."
As the daughter of a fruit and vegetable seller, the 21st seed has appropriately made a habit of upsetting the applecart on her route to the final.
Two former Roland Garros champions, Ana Ivanovic and Svetlana Kuznetsova, were dispatched in earlier rounds, while she came through her semi-final against the highly fancied sixth seed Sam Stosur with a tactical masterclass.
"Maybe my problem always was that I couldn't believe enough to win against the strong players," Errani said after her semi-final victory.
"But now I have beaten three in a row. I'm in the final of a grand slam, so I have to try to think a bit differently."
The petite Errani, however, lacks the physical stature of many players on the tour and the 24 centimetre difference between her and Sharapova will be markedly apparent when the pair stand face-to-face across the net for the pre-match coin toss.
The size difference is a physical manifestation of the chasm that exists between the pair on all forms of the tennis spectrum.
They are both 25 years old, but Sharapova has won $17 million more in prize money and 21 more career titles. The Russian is in every sense a box-office superstar, while Errani is the B movie attraction.
The pair were both at Nick Bollettieri's tennis academy, but it seems even then Errani passed under the radar.
"I don't remember crossing paths," Sharapova said. "We have never played against each other, but I certainly know she's a dangerous player because of the way she's played here and because of the way she's performed on clay this year."
Errani, who has also reached the doubles final at Roland Garros playing with compatriot Roberta Vinci, has found her game perfectly suited to the beaten red brick surface.
A change of racquet to add some extra length to her arm has helped her generate more power on her groundstrokes and the reward has been three titles in 2012, all coming on clay.
But it is the way she manages to make the most of her modest talents that has impressed throughout the tournament, with wily displays of intelligence countering brutal brawn across the net.
"She's hits all the right shots," was Navratilova's analysis.
"She's giving away half a foot, at least, with just one step, if not more, on reach.
"So she's got to make up for that. Justine Henin did it, and now Errani is in the finals. Amazing stuff.
"It takes a lot of chutzpah, so to speak, to think you can compete with players that are a foot taller than you are, but she's doing it."
Sharapova will be keen to show, however, that you need more than just clever shot selection to win a grand slam.
The heart pounding adrenalin and nerve-jangling tension of a major final will be all new for Errani as she steps out on Philippe Chatrier Court, but Sharapova has been there and bought the proverbial t-shirt.
"It's not my first time in this position, but you never know once you get there," the Russian kindly pointed out to her opponent.
"Obviously it's a big moment for anyone, pressure is always part of the game. It has to be. If you don't feel anything then maybe you're not so normal. It's really about how you handle it."