Foster was outstanding for the 1-1 draw at Aston Villa yesterday.
Clarke, who worked with Petr Cech and Pepe Reina at Chelsea and Liverpool respectively, insisted: "Ben is up there with the best of them. Everybody was pointing the finger a little bit the other night but there are no worries about Ben Foster.
"He proved that today - he is a top goalkeeper. Compared to some of the other keepers I have worked with Ben maybe is a bit more unorthodox but he makes the saves just the same.
"In the summer we took all our transfer budget and went after him strongly. We knew in games like this he would make saves which are vital. He made one save in the first half off a deflected shot which was unbelievable."