Eberle will likely have the most impact after Mcdavid, even if they all end up on the same line. Eberle is clearly the second most talented forward on the roster and the only player on the team with any proven ability to carry a line, but the lack of dimension to his game along with his lack of ability to make an impact when the physicality gets dialed up will always hold him back.
Lucic, RNH, and Pouliot are complimentary forwards who are incapable of driving offense on their own, leaving Drai/Puljujarvi as the lone threats to become impact players without depending on someone else to carry them, but that exists entirely as potential and is likely several years down the road from being realized.
Pretty slim pickings after that though. Would be nice if one of the defensemen could step up into that status, but it's unlikely with the current roster of D.
