Initially, all we and everybody else watching were concerned with was the horrible non-call by Michael Oliver on David Ospina. With the ball getting cleared off the line, the Arsenal goalkeeper probably would've escaped a red card, but it surely should've been a penalty.
Unfortunately, that's not where our concerns end. At half-time, as the incident was replayed and analyzed, we saw the shocking images of Oscar exhibiting classic concussion symptoms after the contact with the goalkeeper. That contact appeared to be just a body check live, but on replay, it became apparent that Ospina's head made tremendous contact with Oscar's chin. That the Chelsea player suffered a potential concussion is unsurprising.
Jose Mourinho told Sky Sports that Oscar has a possible concussion. The Brazilian is heading to the hospital.
— ESPN FC (@ESPNFC) April 26, 2015
At this time, we don't know anything for sure other than what Mourinho related to reporters. Didier Drogba was brought on at the break and Oscar has been taken to hospital (he did finish out the first half, which, in hindsight, is not great).