Anyone who is advocating for trading one of the core 4 is advocating for a blow up regardless of what they wanna call it.
Nobody "retools" by trading one of the guys considered part of the core.
If you trade Marner and keep everyone else, you now have to replace ~100 points worth of production, your best PKer and one of the best two way wingers in the league. That's not gonna be done by getting a merely good defenceman, a good forward and a 1st rounder (unless that first rounder ends up being Bedard).
Trading Nylander? Your top 6 is now Matthews, Marner, Bunting, aging Tavares and Mikeyhev (Nylander's cap clearing would allow us to keep him) and Kerftoot?
Trade Matthews? This is out of the question.
Trading Tavares? His contract makes this an unwinnable trade.
Really the only member of the core you can trade and not consider it a blowup is Rielly.
Trading any combination two guys means blowing it up.