Kurt Zouma will miss at least six months with a torn ACL in his right knee.
Zouma leapt beyond Marouane Fellaini and his right leg buckled grotesquely as he landed.
Juan Mata led the appeals for a medical staff to immediately come onto the field.
Zouma will miss Euro 2016 for France and the rest of Chelsea's season.
“Scan today has shown I injured my ACL,” said Zouma on his Twitter feed. “I will have surgery this week and will come back stronger.”