Man-of-the-Match Niemi watched the sending off from his Saints goal and claimed referee Steve Bennett made a grave mistake.
"The referee made a mistake. It was obviously the defender's fault and the defender (Alpay) should have been punished," declared Niemi.
"It was very hard on Peter. I feel for him."
Turkish international Alpay did appear to be the villain tugging Brett Ormerod's shirt and bundling him to the ground but match official Bennett defended his decision to brandish a red card to Enckelman.
"This wasn't a case of mistaken identity. Although I can understand how some people thought it was," said Bennett.
"I understand that Alpay also had a tug, but I didn't see that.
"I can only act on what I saw and I sent off the goalkeeper for holding and pulling back (Brett) Ormerod."
Under-fire boss Graham Taylor revealed the club would not appeal against the ban, adding: "There is no point us wasting our time. Peter will miss the game against Fulham on November 9."
