The club posted photographs of the pair working with their team-mates at its Cobham training headquarters on Wednesday evening.
Keeper Mendy was replaced by Kepa Arrizabalaga at half-time in Sunday's 2-1 Premier League defeat at Aston Villa after suffering a rib injury when he collided with a post.
Midfielder Kante missed that game as a precaution after limping out of the 2-1 defeat by former club Leicester five days earlier with a hamstring problem.
The Blues face domestic champions City at the Estadio do Dragao in Porto with the biggest prize in European club football at stake.
The sides have already met three times this season with Chelsea winning twice, Hakim Ziyech's goal securing a 1-0 FA Cup semi-final win on April 17 and Ziyech and Marcos Alonso firing them to a 2-1 league victory at the Etihad Stadium on May 8.