Henderson completed his £20 million move from Sunderland yesterday.
Comolli told liverpoolfc.tv: "It is very difficult to believe you are talking to a 20-year-old. You think you're talking to a 25-year-old. He's very passionate about football, very committed, a top professional. He's the type of player who'll stay behind after training and do extra work. When you talk to him it's not about money or anything related to off the pitch.
"Everything is on the pitch: where am I going to play, have I got a chance to play, where can I develop most as a player. Kenny and I were very impressed with that and his commitment and passion for the game.
"Oh yes, he is definitely a player for now. Obviously it's up to Kenny to decide but we see him as a player for now. In all the talks Kenny had with him he said, 'If you come you will be very, very, very much a part of my plans.' We know we are building for the future, a bit like with Luis and Andy in January, but we are also signing a player who is going to be effective from day one."