Celtic manager Brendan Rodgers claimed he had little option but to sanction Moussa Dembele's switch to Lyon in order to protect the culture that has been created at Parkhead.
The Scottish champions accepted an offer reported to be around the £18million mark 24 hours after rejecting the French club's advances.
Dembele appeared to hit out at Rodgers on social media in the intervening period and the France Under-21 international was told to leave the training field 15 minutes into Friday's session following a chat with his manager.
The club later confirmed they had accepted an offer from Lyon and Rodgers set out their reasons.
In a statement, he said: "Every decision we make at Celtic will always be in the best interests of the club and our supporters.
"It is vital to make clear that we have never promised any player that he can leave the club at a particular time. It has never happened. In fact, we have said all along that we did not wish to sell Moussa, given the circumstances within the transfer window and that is why we rejected a significant offer yesterday.
"However, this particular decision to accept this offer has been taken in order to serve the best interests of the first-team squad, my coaching team and the culture and environment we have created in these last two seasons.
"The board and myself are united and they have been very supportive to me on this issue.
"Our real focus now turns to Sunday's match and beyond, working with our players here who are committed to doing all they can to ensure another successful season for the club.
"Finally, I would like to thank Moussa for his contribution in our last two seasons and want to wish him well in his new adventure at Lyon."
Dembele sat out Thursday's Europa League win over Suduva following negotiations between Celtic and Lyon, and Rodgers admitted on Friday afternoon that it was "highly unlikely" he would be in the right frame of mind to face Rangers on Sunday.
That statement came after Dembele unleashed several cryptic posts on his verified Twitter account and liked a number of others which backed his stance and criticised the club.
The first post late on Thursday night read: "A man, without his word, is nothing. A real man keeps his word."
The France Under-21 international added in the early hours of the morning: "Don't get it wrong Bhoys and Ghirls nothing to do with people who really care about the club @CelticFC too much love and respect for you and the crest #CarefulWhoYouCallTheLeaderOfYours"
One tweet Dembele liked came from a French media outlet which claimed Rodgers had told Dembele in January that Brighton were a better club than Celtic and tried to convince him to join West Brom.
Rodgers denied the claim "150 per cent".
"I find that hard, being a Celtic supporter and knowing the size of this club and the worldwide appeal, that I would even consider saying anything like that," Rodgers said.
The dissent in the ranks came after Dedryck Boyata had a similar huff after Celtic rejected an offer from Fulham for his services. The Belgian is now back in the team after missing several games when Rodgers claimed he was fit.