Chelsea were forced to substitute Oscar during the derby against Arsenal after their creative midfielder suffered 'possible concussion' in the first half. The Brazilian collided with an onrushing David Ospina in the 16th minute at the Emirates Stadium and was sent to hospital at half time for checks. It looked as if the Arsenal goalkeeper had given away a penalty, but referee Michael Oliver waved away Chelsea's protestation following the painful clash. Oscar was clattered into by Arsenal goalkeeper David Ospina during Sunday's London derby . Sky Sports revealed that Jose Mourinho said the Brazilian was taken off due to 'possible concussion' Oscar was knocked back by the goalkeeper but Michael Oliver didn't award Chelsea a penalty . Didier Drogba replaced Oscar at the break, with Sky Sports revealing that Jose Mourinho had told them the decision was taken because of concussion concerns over the latter. It means Oscar played on for half an hour before being properly assessed, potentially bringing the concussion debate into the public domain again. 'He went to the hospital at halftime,' Mourinho said. 'We are waiting. We don't know yet (if it's concussion).' Television pundits Jamie Carragher, Graeme Souness and Thierry Henry were all in agreement that it should have been a penalty. Carragher said: 'It was a definitely penalty. It could even be a red card.’ Henry said: 'The adrenalin will sometimes bring you back to the field. Maybe he thought he could not go back on after sitting in the dressing room for 15 minutes.’ Oscar appeared in a bad way immediately after being poleaxed by the Gunners' goalkeeper . He attempted to get up but his arms fell back down to the turf in direct response to the hit . The collision was in the 16th minute but Oscar still manage to play on until half-time .
Chelsea weren't awarded a penalty for David Ospina's clash with Oscar .
Arsenal goalkeeper clattered Oscar inside the box .
Brazilian was taken off at half-time, with Didier Drogba replacing him .