Well I'm not sure, just speculating...Well, the young established roster player would be kind of hard. Thompson, Walman (D) Kyrou, or Kostin (top prospects) and a 2nd rounder could cover the other two? The Blues don't have a first for this year I wouldn't want to lose 2 first round picks consecutively, so maybe a 2nd (next year) and 4th (this year)? This is kind of where it hurts losing Fabbri.
But Pacioretty is the Habs captain, has been one of the most productive goal scorers in the NHL the last 6-7yrs, he's on a great contract, the Habs don't HAVE to trade him.
It's not going to be cheap.