I don't agree with Gaudreau as a comparison. If Keller actually enters the league as a Calder finalist, with no softmore slump, and just keeps rolling as the face of his franchise, than I think he will haev been undervalued by many because those are some tall expectations. Seems like an overvaluation of Keller this early.
Similarly I think comparing Guentzel to Brassard is undervaluing him at this time. Guentzel is no where near as gritty and seems to have a superior hockey sense and awareness. He has the skill to put up points in any top 6 scenario IMO.