After Celtic succumbed 2-0 to Rangers in the Old Firm, Neil Lennon was left to rue a leak in the Hoops' camp that undermined match preparations.
On Saturday morning, a copy of Celtic's teamsheet was doing the rounds on social media, leaving Lennon fuming on the day of the game.
Neil Lennon on Celtic leak
Lennon promised a full investigation by Celtic into the source of the leak, and was visibly angry at the events.
"People can make it out to be whatever they want it to be," Lennon told Celtic TV.
"It has been disruptive with Covid, and it has been disruptive with some of them being away on international duty - I am not sure some of them are on the ball today, mentally.
"It is not great. Somebody within the club is doing us in and it's disgusting I think.
"We will try (to get to the bottom of it). We will work on it, but it is very disappointing.
"Of course it makes my job more difficult. I keep talking about a sense of privacy around our club but it doesn't seem to be the case with some people and it's very, very disappointing."
Lennon on Rangers loss
Celtic lost out due to a strike from Connor Goldson in each half, while Lennon rued the changes that Celtic had to make due to international commitments.
"You don't want to play too much on that and look for excuses, but you have three strikers in [Albian] Ajeti, [Leigh] Griffiths, and [Odsonne] Edouard that are not fit enough to start the game.
"We missed a lot of quality today, but we still had a good team out there and should have done better, we should have been at least level at half-time - we just looked like we had run out of ideas."