Spireites skipper Evatt claimed he was attacked by Lilywhites supporters during a pitch invasion following the final whistle of the game at Deepdale which the home side saluted 3-0 to reach the play-off final.
Evatt, who previously played for Preston's Lancashire rivals Blackpool, tweeted "To be attacked on a football pitch and fear for your safety is an absolute disgrace I was punched kicked and spat on several times #disgrace."
Chesterfield's assistant manager Leam Richardson also lashed out at the Preston treatment of their player.
"Obviously there is the rivalry, you can't underestimate that, because that makes football but to lay hands on people as supporters and men I think it is a disgrace," Richardson said in the Lancashire Evening Post.
"Ian is fine. Categorically no, he did not react.
"When you are surrounded by a few thousand people but not sure where you are. He's in there. He's an emotional kid anyway. But he has conducted himself very well.
"We are firstly disappointed with the outcome of the two legs and then disappointed with the outcome of a certain few individuals.
"The police are involved, they are speaking to Ian now. They will be investigating."