The 23-year-old Brazilian was involved in a heavy collision with Arsenal goalkeeper David Ospina during the first half of the Blues’ 0-0 draw at the Emirates on Super Sunday and was taken to hospital for checks.
Oscar appeared to take the full force of Ospina’s head against his right cheek as he attempted to lift the ball over the advancing ‘keeper towards goal in the 16th minute.
The attacker appeared significantly dazed after the collsion and received lengthy treatment by both the club’s physio and doctor before being allowed to play the rest of the opening half.
But he was eventually substituted at half-time and replaced by striker Didier Drogba, before Mourinho told Sky Sports‘ touchline reporter Patrick Davison of the possible extent of his injury.
And the Chelsea boss told Sky Sports at full-time: “We had to change things because of Oscar’s injury. He went to hospital to have some scans and see what is going on because at half-time we were a bit scared. We don’t know yet if it’s concussion.”