Going with Sproul for this one.
No one else left on this list has any legitimate NHL potential.
Jensen is 25. Everyone seems to love this guy, but if he had some potential he would've been in the show a while ago. He's played in the NCAA for 3 years and has over 100 games at the AHL level. If he was good enough he would have forced managements hand already.
Turgeon is almost 20 and this is his first year putting up decent numbers. You think someone in their 19-20 yr season would put up better numbers than 1.0ppg. Career .55 in the dub is very disappointing even considering the fact he played behind other players. For example Mantha, AA, Bert etc. had much better final CHL seasons. By a long shot too. I assume management hoped he could somehow play like his father (which is why I'm sure he had a "First round grade"). I doubt he sticks at the pro level long, if he even makes it that far (Name recognition should help him in that department).
Zach Nasty can barely even crack an ECHL roster, nevermind the Griffins. At best he's a Joakim Andersson type.
Frk can barely skate. Great Shot but that's about it. He's almost a poor man's Pulkkinen. He'll make a great first liner for GRG or he'll go back to Europe and dominate over there.
Coreau is the only player left on this list, besides Sproul, who has NHL potential. Not sure what Coreau's potential is considering he just started playing well this year.
Sproul has really improved on the backend and it's not like his offensive game has/will disappear/ed. He has very good size, and skating. Still a good puckmover. He will definitely make the NHL in some capacity, whether that's as a top pairing guy or bottom pairing guy is up to him.