Paris - Stade Francais scrumhalf Jerome Fillol was cited on Monday for having spat at Bath counterpart Peter Stringer during Saturday's Challenge Cup quarter-final, the European Rugby Cup (ERC) said.
The 35-year-old has been cited for an "action that goes against the spirit of sport" the ERC said, adding that he could face a suspension of between four and 52 weeks.
Television images from the match at Bath's Recreation Ground showed Fillol spitting in the former Ireland scrumhalf's face.
On Sunday, Stringer, also 35, wrote on Twitter: "Disgusted at what happened yesterday in the game. No place for it in rugby or any walk of life."
Stade's prop Rabah Slimani was also cited for a dangerous tackle that earned him a yellow card during the game.