Blues decline. Buch has a cheaper salary and is under control for longer

The Blues don't say anything, they just make this face:

Not to mention the Rosen for Rutta dump.

Wow. Let's look at the players involved:

Buchnevich - A decent but overpaid 3rd line quality guy. Reminds me of Granlund (yes the stats back that up).
Rosen - An ok 4/5 defenseman
Guentzel - A great possession player who scores 35 - 40 goals (on 1 year left)
Rutta - An overpaid 7/8 defenseman
The first trade is terrible for Pit

Kulak - An overpaid 4/5 defenseman (if he is healthy)
POJ - A young (currently) 4/5 defenseman
DeSmith - A fine backup goalie
The second trade is bad for Pit.

These aren't good trades for the penguins. You can get much better for Guentzel, and the Kulak trade is a loss for the penguins.

Looking at Kulak's stats, "17:07 minutes, 3 goals, +3, $2.75m" - dunno why you'd want him.

Oh, sorry, those are Jan Ruttas stats.

Kulak was "17:31, 3 goals, +11, $2.75m"

Goals are always the best way to evaluate a defenseman.