Neither of those players holds interest to the Blues, I'd imagine.

Taking some draft picks, a good prospect and drouin to replace him is not bad at all

Hillis is tiny, and the Blues (who don;t need a center anyway) prefer bigger players (or at least ones they play bigger than they are). The picks are nice, but the Blues are trying to contend now. I cannot imagine the Blues wanting Drouin, who is way too expensive for a guy who'll simply walk away form his team before the playoffs for a mystery reason (and he's a passer, when what they want is a scorer). This is an offer you make to a rebuilding team, and I would bet dollars to donuts that the Blues would scoff at it.