Honestly, I have a hard time believing that if we plugged Puljujarvi into McGinn's ice time, that McGinn would outproduce Pulju.
McGinn's career ATOI is 13:33, and he is a regular PKer for the last 3 seasons. Pulju's career ATOI is 12:28 and as far as I can tell he he has never PKed. So that's about even. Pulju gets 40 seconds of PP time per game career; McGinn gets 14 seconds.
Quality of linemates: Pulju's most common linemates appear to be RNH and Strome, whereas McGinn's most common linemates are Wallmark and Martinook.
Age/experience: Pulju is 21 and has 139 NHL games played over 3 seasons. McGinn is 25 and has 240 games played over 4 seasons.
Production: McGinn averages 26 points per 82 games and is a go-to PKer and I think most people here would say he's a decent defensive forward at worst. Pulju averages 22 points a game, does not PK and I'll leave the judgement on his defense to somebody else, but I'm going to make an educated guess and say defense is probably not the strongest part of his game.
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Looking at the above, if I have to give up McGinn in order to get Puljujarvi, I'm not sure that's a very good move.
I suppose what you have to ask yourself is, if you lost McGinn and Puljujarvi was a total bust, can you replace McGinn's role on the team with somebody else already in the system. I'm not sure we have a ready-made replacement for gritty bottom 6er who can hit everything in sight, be a good PKer and also score 25-30 points. And we're not the most free-wheeling offensively explosive team so that kind of player carries a premium for us.
And as much as I'd like to ignore intangibles, because by definition they are subjective, it's hard to ignore McGinn was just now the guy who sold out to stop a puck from going in the net late in a game 7, and then scored the game winner in that same game. He might just have that in his DNA, he could be Justin Williams' Mini-Me. Would suck to trade a guy like that on a reclamation project that didn't work out.
Now, if we can get Pulju for say, a 2nd round pick, or a prospect like McKeown, go for it. Otherwise I don't think the risk is worth it.