Add it to the long list of trades BM has lost to the Penguins. Someone needs to approve his trades with them since its likely going to be lopsided.
I think it's a bit too early to call BM as the loser of this trade. Yes at the moment Pettersson is the better player but Sprong has looked better than ever and he certainly has potential to be an effective top 6 forward.
Also, I had to check into the trade history between Anaheim and Pittsburgh when BM has been in charge and I don't see many lopsided deals.
Kunitz and Tangradi for Whitney - Kunitz was probably the best player in this deal but his numbers were inflated by playing with Crosby for so long while Whitney was useful but not great
Rights to Modig for 2010 6th round pick (Lind) - Whatever trade for both sides
2014 5th round pick for Lovejoy - Lovejoy became a great partner for Fowler
Zolnierczyk for Alex Grant - Whatever trade
Lovejoy for Despres - Despres became great until the injury but was definitely better than Lovejoy
Hagelin for Perron and Clendening - Great trade for Anaheim getting rid of Hagelin and his contract and acquiring Perron
Pettersson for Sprong - As I said, not looking great now but time will tell
Blandisi for Derek Grant - Grant is great
Martinsen and 2021 7th round pick for Gudbranson - Gudbranson has been solid addition and not much was lost for him
Honestly, I would say that BM has done well in these trades. If Despres hadn't gotten injured, that trade would have been a robbery. So unless I missed some trades I don't think there's a long list of trades that BM has lost to Pittsburgh.