The 27-year old centre-back will return to Nottingham Forest for a fee of £2.5million, citing family issues as the reason, and he says it is very tough to depart the Scottish champions.
"I have one or two things to resolve and I've been in constant contact with the gaffer (Neil Lennon) all week," said Wilson.
"He knows I am not looking to leave for football or financial reasons. If I am to leave it will be for family reasons which I'd rather not go into.
"But it will be difficult to go, you just need to look at occasions like tonight. European football and the Champions League are massive draws and you just need to think back to last season.
"But I am leaving for personal reasons and the boss understands that. It's personal but people that need to know, we all know and understand."