Last season Liverpool could reach the Champions League final stage and were stopped by Real Madrid in the final (3-1).
Two errors from goalkeeper Loris Karius helped the Spanish side on their way.
Karius collided with Real Madrid defender Sergio Ramos and five days later he was discovered to have 26 of 30 markers for a concussion in tests.
Jurgen Klopp also confirmed in his interview with BBC Sport that the German keeper had concussion.
Klopp added: "Nobody believes what happened in Kiev but it is 100% true, he had concussion.
"Anyone who has had it knows it is quite difficult to judge situations. You have forgotten things and other people have to tell you how you behaved. That how these things are but the world out there is not interested.
"I really think that Loris is our goalkeeper 100%. From that point of view nothing changed. Is this the most easy period of his life? For sure not. Can it make him stronger? 100% yes.
"He is still a young boy. He has outstanding skills. The big goal is to bring it out on the pitch. That is the way it is for all players. We will try to help him with that."
Liverpool continued their pre-season US tour with a 2-1 win over Manchester City and face rivals Manchester United on Saturday (22:05 BST).
They play their opening Premier League match at home to West Ham on Sunday, 12 August.