They would have had time to get someone good if they wanted to recast him.
So yes, rather then having Peter show up and think he's Jeff, but has amnesia, I would have liked them to bring Burke back.
They never explained about who Jeff Clark was. Was he someone whom Peter possessed? And what about what Dr. Lang said about him having killed someone or something? I can't remember exactly what it was. But I remember he said something about him having been a patient in a mental hospital for the criminally insane.
If Peter was simply possessing someone, how did he happen to find someone that looked just like he did?
Misa