West Ham take on City after the international break and Allardyce is already eyeing another surprise success.
"They can be beaten," he told the club's official website. "Aston Villa and Cardiff have beaten them, so we take confidence from this result.
"We'll play a different way at home after the international break and we'll try to go out and win the game.
"They have lost two away from home and conceded five goals in those two games, so there is an opportunity there to capitalise on."
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