Willemse, 28, was given a red on Saturday after appearing to come into contact with opposition support Wyn Jones and will learn of the Six Nations panel result on Tuesday evening.
“Paul is stressed. It was an accident. He thought it was the other player’s shoulder, unfortunately his hand was in the wrong place, ”said South Africa-born second row Le Roux.
“We will know more tonight. He told me last night that he barely slept. Her stomach is in a knot. I am disappointed for him, ”he added.
Racing 92’s Roux have missed the Blues’ two previous matches with a thigh injury, but are expected to play the title decision maker role on Friday at home against Scotland.
The hosts will win their first trophy since 2010 scoring four or more tries in a 20-plus point victory.
His compatriot Romain Taofifenua is in doubt for the match but with a knee problem suffered this weekend.
“I’m fine, I have no pain. We have a huge game now, ”said Le Roux.
Half-driver Romain Ntamack is expected to start in the French capital with Matthieu Jalibert absent after suffering a blow to the head.
Le Roux, 31, will face Finn Russell, who also plays for the Parisian club, at the Stade de France.
Influential flyback Russell was sidelined with a concussion after scoring 10 points in the loss to Ireland on March 14.
“He’s a very difficult player to analyze, even if you play with him,” said Le Roux.
“You never know what he’s going to do, even if you play on his team. We will put pressure on him. If he is confident, he plays better, ”he added.
On Sunday, Stade Français announced that French center Gael Fickou would leave them with two years of his contract remaining for local rival Racing at the end of the season.
“My reaction is simple. I am sad to leave my Stade Français teammates but happy to join those of Racing, whom I know very well having played in France and in Paris, ”said Fickou.
“Originally, it was not a decision made by me. It was a tough decision to make. It didn’t distract me at all from my preparation with France. “