"Craig is now at a good age - 27 - which is not old but he has a lot of experience under his belt," said the former Liverpool striker.
"He is a very ambitious person and I think he is really looking forward to the challenge of playing for Liverpool.
"He has always supported the club and although he has had Premiership experience with Newcastle and Blackburn, the expectation levels at Liverpool are greater than anywhere else.
"He'll need to come to terms with playing Saturday, Wednesday, Saturday, even though Rafa likes to change things round a bit and always has one eye on the games that lie ahead.
"Craig probably won't play in every game but he'll probably be used in one or two different positions. The thing is that he has gone to Liverpool to win trophies, which is what every player wants.
"I think he won a cup medal at Celtic, but otherwise the sideboard is bare, so he has a very interesting challenge in front of him. But the main thing is that he is happy and this is a move he so obviously wanted."