Many supporters booed at the final whistle at Eastlands on Saturday but Cook said: "The fans are at the centre of what we do and they are entitled to their opinions. They pay good money and you should be open to that criticism - and we are.
"But they should feel good about the fact we are going to build this thing into something quite special.
"Mark has played and managed at the highest level and knows what success looks like.
"He and I talk about that success all the time and we are not standing there thinking about 'what if'.
"We are thinking about when we become successful and how that'll look."