"I played against Berbatov at White Hart Lane last May and we not only won but kept him fairly quiet," he said.
"That doesn't mean the same will necessarily happen this time. You can't make assumptions like that about someone of his quality.
"He is a significant signing for United and will make them an even greater force to be reckoned with. Our task is going to be harder than ever now, but we are more than happy with what we've got up front at Liverpool.
"I wouldn't swap Fernando for anyone, because I have seen more than enough of him over the past year to know he is the best striker in the Premier League. There are plenty of good ones, Berbatov included, but Nando (Torres) is top of the pile.
"I'm just grateful I don't have to face him in matches. It is bad enough on the training pitch. You would struggle to find a striker anywhere who has so many attributes. Pace, strength, technique - it's all there.
"And he can finish from any distance or angle. He is always liable to come up with something different or produce a moment of brilliance that settles a game - so often, you just don't see it coming."