You don't do it because he's slumping. You do it because in a trade, you have to give to receive. Nobody is giving him for a 7th rounder. If you want to get a Kreider and somehow the Rangers want a roster player, tell me who you are giving? You are giving him 'cause he's the most expendable while having surely some kind of value. I'd give Drouin ahead of him. But I think most teams would/should/will get away as fare as they can from that kind of player. So if not Drouin or Lehkoknen, tell me which roster player we could do without? Sure, Lehkonen could rebound as I would expect him to do.....but the player we should be getting is not scheduled to be a 4th liner either.
I'd trade anyone for the right price but certain players that price would be very high for players like Kotka, Brook. I'd be all for trading Drouin if the price was right, if we could package him for an upgrade, someone like Huberdeau. Leks if the price was right I'd trade him but I wouldn't be in a rush to trade anyone, we clearly aren't good enough to go very far this year and I would expect us to be around the same next year. What we need is guys like Kotka, Brook, Suzuki, Poehling, etc... to come in and be as good as we think they are. I don't see UFA's or trades that are suddenly going to put us on the same track as TB, leafs, etc..
I wouldn't have any interest in Kreider, he just doesn't move the needle much at all. But I prefer to sell high on guys, trade them for peak value. Petry, Domi, Tatar, Drouin, Danault, all having career years, strike while the iron is hot, not all of them of course but if the deal is right where we can get a high end player that is still young enough to be an impact player in a few years when hopefully Kotka, Brook etc.. are starting to become impact players for us.