Jurgen Klopp was left worried seeing Marko Grujic hospitalised following a collision with Bertrand Traore in Liverpool's International Champions Cup defeat to Chelsea on Wednesday.
The Serbian midfielder has impressed in pre-season after linking up with Jurgen Klopp's side for the first time, following a January move from Red Star Belgrade, but the 20-year-old, who spent the second half of 2015-16 on loan at his former club, had to be withdrawn at half-time in Los Angeles.
And, speaking after his team's 1-0 reverse, Klopp revealed he is yet to learn the full extent of the damage in a situation he described as "not cool".
"The biggest problem for me in this moment is that Marko Grujic is in hospital, because he can't remember anything," he told the media. "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."
However, there was better news for Liverpool regarding two other new signings.
Ragnar Klavan was on the end of a bad challenge from Cesc Fabregas in the 70th minute, but he appears to have avoided injury.
Meanwhile, Joel Matip missed the game with an ankle issue, but Klopp is hoping to welcome back the former Schalke defender soon.
"I expect him to start the season," the Liverpool boss said of Matip. "But for this, he has to train a little bit more.
"The first two-and-a-half weeks were really good, he became better and better and then he was out.
"Now I think it is a week or more he has been out.
"He was in a training group today and hopefully he can be back in team training as soon as possible.
"The season start at this moment is not in doubt."