Dunfermline Athletic have asked police to probe a death threat against goalkeeper Derek Stillie.
Derek Stillie was beaten six times by Rangers at Ibrox
And club chairman John Yorkston has blamed Celtic for failing to put a lid on the fall-out from an explosive last day of the Scottish Premier League season.
Rangers' 6-1 win over Dunfermline allowed the Ibrox outfit to take the title from Celtic on goal difference.
And Celtic striker Chris Sutton accused the Pars of lying down to the new champions.
Celtic face Dunfermline on the opening day of the new league season and some Hoops fans plan a "lie-down" protest at East End Park on 9 August.
Dunfermline chairman John Yorkston said: "We thought it had been swept under the carpet, but this latest letter just keeps the thing going.
"The letter was handed over to the police, but it is scary when it mentions your family.
"I would think Derek got over it. However, I would also say that I don't think things like that ever leave your mind.
"If you were to get an anonymous death threat then you might say that was a
prank and 90% of you would say it was just an idiot, but there will always be
this wee element of doubt in your head.
"Nobody from Celtic has ever apologised directly for what Sutton said. Sutton did it first through his agent and then via the club website.
"If Celtic had made a statement distancing themselves from the remarks, this nonsense would have been avoided."
Dunfermline will step up security for the season opener and have taken steps to protect Stillie from hate mail delivered to their ground.
However, a potential flashpoint will be avoided on 9 August, with Sutton suspended for the game.
Sutton later apologised for his comments but has hired a specialist sports lawyer to fight the Scottish Football Association ban for bringing the game into disrepute.
Meanwhile, Yorkston disclosed that he too had personally experienced problems.
"A car load of Celtic fans turned up at my street after the game and I went off to Magaluf immediately after the Rangers game, but one of my neighbours had a fight," he said.
"I wish I was joking about this, but he had to chase them off with a garden spade.
"I am 6ft 6ins, but it's worrying that this is in anybody's head.
"I wasn't there and was on holiday and I heard about it a few weeks after the
event, so what do I say after that?"
A Fife Police spokesman said: "I can confirm that we are investigating a certain letter in respect of Dunfermline.
"Enquiries are at a very early stage."