Quoting: leafs_and_devils
sda is a future middle 6 winger so i feel like him and a 2nd are worth at least a first if not more
You seriously overestimate the value of a prospect and a second (which is not close to a first), and the value of Der-Arguchintsev in particular.
Let's consider just the winger prospects of some crummy teams (i.e., much weaker than the Maple Leafs):
Seventh-worst team in the NHL last season: Lias Andersson, Samuel Fa.gem.o, Arthur Kaliyev, Rasmus Kupari, Akil Thomas -- excluding top-6ers Alex Iafallo, Adrian Kempe, Dustin Brown and Viktor Arvidsson and center prospects Quinton Byfield, Alex Turcotte and Gabe Vilardi -- SDA doesn't replace any of those middle-6ers.
Second-worst team in the NHL last season: Isac Lundestrom, Jacob Perreault, Brayden Tracey and Sam Colangelo -- excluding top-6ers Max Comtois and Troy Terry and center prospects Trevor Zegras and Mason McTavish -- SDA isn't likely to crack the middle 6 of that group, either.
Even the hapless Buffalo Sabres have a better middle-6 winger prospect pool: Jack Quinn, John-Jason Peterka, Rasmus Asplund, Linus Weissbach.
In short, SDA isn't a future middle-6 winger unless he makes substantial progress from where he is now.