Assuming that the bolded word is winner, the correct answer is object complement.
The word winner refers to the word <em>play - </em>and given that the word play is the direct object of this sentence, then the word <em>winner </em>will be its complement - it will complete it, and answer the question What did the critics declare the play to be?
It cannot be a predicate nominative because it is not preceded by a verb. It cannot be a direct object because that is <em>the play. </em>It cannot be a predicate adjective because it is a noun, not an adjective.
