Along with manager Paul Ince and assistant Alex Rae, Thompson was ditched by the Championship club on Tuesday.
Veteran midfielder Barry Ferguson is set to be in charge for Saturday’s clash with Doncaster.
Thompson joined Blackpool in 2005 and helped them to promotion under Grayson, who is now in charge at Preston.
And Grayson said: “He deserved a little bit more respect than getting sacked by a text message. Karl might regret that because Thommo has done everything for that club from coaching the youth team and the first team to picking players up and washing kit .”
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