Porto defender Nanu was knocked unconscious and "suffered a spinal cord injury" in a sickening collision in a Portuguese top-flight match on Thursday.
An ambulance had to come onto the pitch at Belenenses to rush the player to hospital after an accidental clash with home goalkeeper Stanislav Kritsyuk.
The incident happened in the 85th minute of the 0-0 draw as Guinea-Bissau international Nanu chased a cross into the penalty area.
He was treated on the pitch for 15 minutes with some players in tears on seeing the stricken star.
"Nanu had a cerebral concussion and spinal cord injury with a loss of memory," Porto later tweeted.
"At this moment, he is stable, conscious and is aware of time and his surroundings."
Porto's veteran star Pepe was one of the players left distraught as Nanu lay motionless on the pitch.
"I wish our teammate Nanu a speedy recovery. The doctors in the ambulance told me that he was doing well, that he was already conscious," the former Real Madrid player told Proxima Jornada in the aftermath of the game.
