At 29 Hamann is one of the more senior members of the squad, with World Cup experience and a spell at Bayern Munich to boot.
And it is the composure in the German's play, plus his reading of the game, that makes him such a pivotal part of the current Liverpool setup.
Houllier said: "Didi is a very experienced midfielder whose composure helps us enormously.
"We have a young squad, a young team and it is good to have someone like Didi who reads the game well and brings out the best of the players around him."