Scans reveal Liverpool goalkeeper Loris Karius sustained concussion during the Champions League final defeat to Real Madrid in which he made two crucial errors.
Massachusetts General Hospital has confirmed the player underwent assessments five days after the 3-1 loss in Kiev.
Karius is on holiday in the United States but Liverpool's medical staff wanted him to be checked out and a subsequent examination found evidence of concussion, which doctors say could have affected his performance.
The goalkeeper was caught in the head by Sergio Ramos at a corner before Madrid's opening goal, which was the first to be blamed on Karius.
"With Mr Karius's permission we are providing information about his medical situation in an effort to prevent, where possible, the dissemination of incomplete or erroneous information," said a statement from MGH.
Karius was widely blamed for Liverpool's final defeat after his two errors, and Merseyside Police later released a statement saying its officers were aware of "threats" made against him on social media.
The 24-year-old gifted Real the lead when he attempted to launch a quick attack, only for Karim Benzema to thrust a leg out and divert the ball into an empty net.
Karius then allowed a long-range effort from Gareth Bale to evade his grasp in the closing stages.
Liverpool have declined to comment on Karius' situation.