The Manchester United striker hasn't found the target at club level since February, a run that has lasted nine games in all competitions.
However, Van Persie did score three times in the Netherlands' two recent World Cup qualifying games.
De Guzman told reporters: "I'm confident Robin will deliver against Manchester City. He's been delivering all season and he's a world-class player."
Van Persie has scored 19 goals in the Premier League this season.