LONDON -- Chelsea midfielder Oscar was taken to a hospital to undergo checks on Sunday, with the club unsure if he had sustained a concussion after colliding with an opponent during the Blues' match at Arsenal.
The Brazilian was injured around 15 minutes into the 0-0 Premier League draw when Arsenal goalkeeper David Ospina clattered into him, making head-to-head contact. Chelsea's doctor came onto the field to attend to Oscar but he returned to action and was only substituted at halftime.
Mourinho reports Oscar went to hospital at half-time. He is waiting to hear the latest. #CFC
- Chelsea FC (@ChelseaFC) April 26, 2015
Mourinho said in a postmatch interview on Sky television that Oscar "went to hospital to [have] some scans to see what is going on because at half time we were a bit scared."
When asked in a news conference if Oscar had suffered concussion in the collision, Mourinho replied: "I don't know."
Before this season, the English Football Association tightened the regulations for the management of concussion.
Players should be taken off the field of play and not allowed to return if there has been a "confirmed or suspected period of loss of consciousness," the FA rules say. Club doctors were given the final say on whether a player stays on the pitch after a head injury.
In the reverse fixture at Stamford Bridge in October, Chelsea goalkeeper Thibaut Courtois was suspected of being concussed after his head was hurt in a collision with Arsenal forward Alexis Sanchez.
At the time, Chelsea was criticized for allowing Courtois to play on for around 10 minutes before being substituted. The Belgium international went to the hospital as a precaution but was later given the all-clear for concussion and was only treated for a minor cut to his ear.
In a high-profile incident last season, Tottenham goalkeeper Hugo Lloris was allowed to return to the pitch by then-coach Andre Villas-Boas during a Premier League match against Everton after appearing to lose consciousness when he was struck on the head by an opponent's knee.
Questions were raised during last year's World Cup about the management of concussion when Uruguay defender Alvaro Pereira ignored his team doctor's advice to be substituted. Pereira appeared to be briefly unconscious when accidentally struck in the head by an England player's knee.
Then in the World Cup final, Germany midfielder Christoph Kramer played on for 14 minutes against Argentina before being substituted when clearly disorientated.
FIFA has since allowed matches to be stopped for three minutes while team doctors assess players with head injuries.