Warnock picked up a knock on his ankle which a scan has revealed is nothing more serious than heavy swelling. Warnock left Anfield on crutches after the match.
Hamann picked up a medial ligament strain and Morientes has a thigh problem. Luis Garcia also injured his ankle.
Talking after the game, Rafael Benitez said: "We need to see how the injuries settle down now.
"Maybe they will all be out for two or three weeks. It's hard to say at this stage but clearly we have a lot of problems at the moment.
"I am so proud of the players for the way they coped with the situation. It was a very difficult game and this is such a good win for us. We played with a high tempo in the first half and definitely deserved our victory."