Drogba was knocked out in a collision with Canaries goalkeeper John Ruddy and was carried off on a stretcher using a breathing aid after receiving seven minutes' treatment at Stamford Bridge. Drogba remained unconscious "for quite some time", Andre Villas-Boas said afterwards, confirming the 33-year-old had been taken to hospital. "We are just waiting for the full exams on his concussion and hopefully nothing is wrong," Villas-Boas said. "He is showing some good signs of recovery for us to be a little bit more tranquil." Villas-Boas had no problem with Ruddy's challenge but said of the incident: "It looked pretty nasty. "He lost consciousness completely on the pitch. "I have to be very, very grateful, not only to my players but to the Norwich players and to my medical staff for reacting so quickly to a potentially dangerous situation."