Liverpool midfielder Marko Grujic has been taken to hospital with suspected concussion after a clash of heads during his side's 1-0 friendly defeat to Chelsea.
The 20-year-old, who joined from Red Star Belgrade in January but has linked up with the Reds squad just this summer, collided with Blues defender Bertrand Traore towards the end of the first half of the International Champions Cup clash in California.
Midfielder Grujic was then substituted at the break before being sent to a medical facility for checks following the aerial challenge.
Klopp told his post-match press conference: "The biggest problem for me in this moment is that Marko Grujic is in hospital, because he can't remember anything. That's not too cool.
"Hopefully it's not too serious but of course a young boy in this situation is not too cool. Injuries after games like this in pre-season is the biggest problem obviously."
The game at Pasadena's Rose Bowl was an intense and feisty occasion, with Chelsea midfielder Cesc Fabregas being shown a straight red card for a second-half challenge on Ragnar Klavan.
