The Brazilian playmaker, who has scored six goals in all competitions this season, is reportedly facing more than a month on the sidelines.
The 24-year-old was stretchered off the pitch around half an hour into Liverpool's 2-0 victory over Sunderland on Saturday afternoon.
"Of course it's not nice to see your teammate and so great a player go off injured like that," the Liverpool Echo quotes Karius as saying. "In the game you can't worry too much about it because we needed to carry on. I'm sure he wanted us to play well and win the game.
"After the game everyone was asking how he was. We have to wait and see what the doctor says. It's hard to say at the moment how long he will be out. He has obviously done something but we are all hoping for the best.
"We have a big squad and everyone is fresh because we haven't had many games. We change a good player out and we still have high quality coming in. That's a very good sign. Everyone is confident that when we have to change a player, the player coming on keeps the level or even lifts it so that's a really good thing for us."
Meanwhile, the Reds are preparing for Tuesday night's EFL Cup quarter-final against Leeds United.