In his first five matches of the tournament, Federer has played all right-handed players.
But he comes up against the unique test of Nadal and his all-conquering left-handed style.
For years, Federer struggled to deal with Nadal style of play, especially on clay.
Since changing to a bigger racket and playing with more aggression on the backhand side, Federer has won the last five matches against Nadal.
However, none of those matches were on clay where Nadal remains the man to beat.
Well aware of the challenge he faces, Federer said he would undertake specific training to prepare for Nadal.
And this morning, Federer hit the practice court with world No 110 Moutet.
The Next Gen star plays left-handed and has a two-handed backhand like Nadal and Federer will hope to replicate what he will face from the 11-time French Open champion.
Moutet reached the third round at Roland Garros before being beaten by Argentine Juan Ignacio Londero.
Federer has looked to attack the net throughout the tournament and the 37-year-old said he was keen to get practice with left handed players.
“With Rafa, particularly on clay, you have to be aware of his strengths, what he brings to the table. And on top of it, because he’s a left-hander, it just changes everything,” Federer said.
“I have two days, which I guess is a good thing. It’s better than one. It’s better than none.
“So from that standpoint, I get more left-handed practice, more serves and all that stuff.
“Because I guess I have played five guys now that are righties, so for me it’s a complete switch-around.
“Just the way the ball goes out of your strings with the different spins, it’s just different. So you have to get used to that quickly. Don’t have much time to waste.
“That’s why you have to be fearless to some extent to take on the spinny balls, the sliding balls, the kicking balls, and that’s what I will do on Friday.”