Agreed on the Petterson signing. Although I believe they still can use a top 4 D. Letang and Schulz are injury prone players and the 3rd pair is a joke. So even if everyone is healthy the D can use an upgrade.
Even if that D costs 5-7 million but is an upgrade to our current 3rd pair, which is not that difficult, it would be an even trade salary wise. Or almost even