"He can become a Liverpool legend, he can do that. If he went to a Barcelona, a Milan or a Madrid he would have an impact because of what he has - a great work ethic as well as great ability," said the former Wales boss.
"Sometimes his personality grates on some people but as a professional, as someone who comes in to try to better himself every day, you can't fault Craig.
"If you don't know him you don't understand the desire he has to be the best player he can be. I don't think he should ever be knocked for that.
"He did an excellent job for us at Blackburn. We embraced him and he embraced us and what we were about, that's why it worked. Captaining his country was also important to Craig. He likes to be recognised as one of the more important, senior players."