The 28-year-old was signed in a £22 million deal from Rennes last month and instantly replaced Kepa Arrizabalaga as Frank Lampard’s first-choice goalkeeper at Chelsea.
Mendy kept a clean sheet on his Premier League debut last weekend as Chelsea sealed a 4-0 victory over Crystal Palace at Stamford Bridge.
But he could now face a spell on the sidelines after he was forced to withdraw from Senegal’s squad on Thursday due to injury.
The Senegalese Football Federation confirmed that Mendy suffered an injury to his right thigh during a training session on Wednesday.
Mendy was sent for medical tests in Rabat but has now withdrawn from Senegal’s squad and has returned to Chelsea for further examinations and treatment.
Senegal are due to play friendlies against Morocco on Friday and Mauritania next Tuesday.
Mendy, meanwhile, could now be unavailable for Chelsea’s next Premier League fixture against Southampton on October 17.
Speaking about his future earlier this week, Kepa said: ‘I feel good, strong and confident.
‘Maybe it’s not the dream situation, but sometimes these things happen. I am confident I will turn my form around.
‘I do not have the feeling of being a substitute. We have three goalkeepers and the level is very high.’