While Pettersson has been very underwhelming in the playoffs so far, I do think that it's too early to throw the towel in on the guy.
He could use, and I'm sure management is very aware, a linemate that truly compliments his ability. Mikeyev is not that at all. Hoglander can be, but he is getting used to the intensity of the playoffs and should acclimate as things go along. Yesterday, the 2nd line did look quite a bit better, especially Hoglander who was playing more like he used to.
Pettersson's defensive game was sound, but it's his offensive acumen that is the gamebreaking talent that awarded him with the big contract.