I don't think I've read anyone saying Matera's bound to be a champion Raglan. What is clear is that he's got a fair bit of talent and his biggest issue seems to be consistency. The Suns are full of talented but inconsistent players, hence the willingness for them to offload him.
Small forward is one of the trickier positions on the ground, particularly in a team that's struggling. There's a lot of examples where small forwards have really hit their straps in the second half of their careers (particularly at a new club, with a second chance) and gone from flake to shark before most people even notice.