On the face of it her matchup with top seed and defending champion Serena Williams was an experience mismatch.
The 34-year-old American had played 26 Grand Slam finals and won 21 of them. The Spaniard, 12 years her junior, was playing in just her second having lost last year's Wimbledon final to Williams.
Plenty of reasons then for Muguruza, who has suffered from nerves in the past to get stressed out. But French coach Sam Sumyk has been working on her mental approach and that was what she kept firmly in the back of her mind in Paris.
"I have been saying during the whole week to be less emotional. To believe more that I'm here because I deserve my place here. I earned it," she said.
"You know, I played well. I earned to be here in the final. I think just to don't think about other stuff. Just give it all in the court and doesn't matter who's in front, which round it is.
"Just to control the emotions I think is the key sometimes, especially in a Grand Slam where you're very nervous and excited."
Other factors were at work in the Muguruza brain cells as she prepared to face up to a player many consider to be the greatest of all time. Firstly, despite losing in straight sets to the American at Wimbledon she was far from disgraced, putting up a strong showing behind her big serve. And then there were the upset wins over Williams by Roberta Vinci in the US Open semi-finals and Angelique Kerber in the Australian Open final.
"Yeah, I thought about it. I thought about it yesterday. I'm like, Come on. You can do it," she said.
"When you see people that are winning and there's new faces, makes you think like, I can be one of those faces.
"Hey, if Kerber can I can, or whoever is there. Yeah, for sure, it helps to see new faces."
The tournament win in Paris means that Muguruza will rise to a career-best second in the world rankings behind Williams with Wimbledon coming up later this month where she already knows she can compete. It is just a matter of trying to get more consistency into her game and avoid form slumps like the one she underwent earlier this year.
"I think I'm ambitious. I think I have a strong character and I like competition. I like to compete. I like to play against the best players," she said.
"This is a source of motivation for me. I'm very happy, because today I proved to myself that I can play really well, that I can manage my stress and win against one of the best players in the world."