Since this is still a hot topic in the thread I will address it.
Let's take a look at the logic about progression. Interestingly enough, it seems like an appeal to mathematics, which seems solid enough at first glance.
But your argument appears to be that Fiala is improving and Marner is not. Therefore, being that their performances this season are roughly equal, Fiala will be the one to improve or "have the higher ceiling" in the future.
While I accept that this argument is valid, it is most definitely not sound. For anyone reading who is unfamiliar with the terms, here is a quick definition on valid vs sound: "A deductive argument is said to be
valid if and only if it takes a form that makes it impossible for the premises to be true and the conclusion nevertheless to be false. Otherwise, a deductive argument is said to be
invalid. A deductive argument is
sound if and only if it is both valid, and all of its premises are
actually true. Otherwise, a deductive argument is
unsound."
Validity and Soundness | Internet Encyclopedia of Philosophy
Your argument makes sense if the premises are accepted at face value (Marner stagnating and Fiala improving into the future), but I think that neither of those are true, which makes the logic unsound and therefore faulty.
The first major issue that I take with this argument is that Marner can be seen as stagnating. The simplest look at this one is the gap between his 2nd year in the OHL and his NHL numbers. Because I'm feeling cheeky, I'll compare Marner to Sam Gagner. Gagner scored 118 points in 53 games in London, before scoring 49 points in 79 games as a rookie with the Oilers. If we are to assume Gagner as a baseline, then Marner must have improved to reach his total of 61 points in the NHL. If I put aside the cheekiness, Marner's linemates in that year were Tkachuk and Dvorak, who all scored very similar point totals in the OHL and did not put up anywhere near the NHL numbers that Marner did. I argue that your premise of Marner stagnating over four years is simply untrue, which makes your argument unsound.
The second major issue is that you argue that improvement means a higher ceiling. To refute this I will argue that hockey is not a linear mathematical model. Fiala's future is in no way a function of his past. If the guy has a higher ceiling it is because of the hockey tools that he has. It is not logical to think that because he has improved to Marner's level over the course of four years that he will surpass Marner in the future. Combined with your first premise of Marner stagnating being untrue, this makes your second premise untrue and your logic again unsound.
Your argument is unsound due to faulty premises and is therefore incorrect. If you intend to continue with this argument I would suggest that you come up with some new evidence that will make the case for your premises being true.