Every year there's a few players that jump up much higher than they were projected and players that fall much further than they were projected.
Clayton Keller, although unlikely to go sixth, is a possible reach target that could be on the Flames' radar if they're not completely sold on whoever is left to them between Nylander, Tkachuk, Dubois or a top-end defender. Keller is generally thought of as a tier or two below the Tkachuk, Nylander, Dubois group but there are a few arguments for why he might be in the sixth conversation.
Keller is a smooth skating, playmaking centre for the U.