They’d like to save more money. Idk why, go talk to their owner …
According to CapFriendly, Petry is only due $4.5M for the rest of this year ($7.5M total salary and a $3M signing bonus that was already paid out July 1) and he's only due $5M next year. So they'd be getting Petry for 2 years at $9.5M real dollars.
They are still on the hook for $38M in real dollars to Karlsson. If they retained 40% ($15.2M), and added it what they'd owe Petry, it would cost them $24.7M.
Saves them $13.3M real dollars.
They could hold onto him and try again next offseason, but then they'd have paid him $10.5M that he's owed this year and would likely run into the same issue of needing to retain and/or take back contracts next year anyway.
I don't blame them for trying to get a 3rd team involved if they are more concerned about the money than the return, but if they don't find any takers, then they are going to have to shit or get off the pot. Do you want to save $13.3M or wait and see what happens?
FWIW, the savings by year would be:
Year 1 : $1.8M
Year 2 : $1.6M
Year 3 : $5.4M
Year 4 : $4.5M