Celtic failed in a deadline-day bid for Israeli midfielder Maor Melikson.
Wisla Krakow rejected the offer for the 27 year old and the Scottish champions refused to raise their bid.
The player's agent, Dudu Dahan, admitted Melikson was upset the proposed move failed to go through.
"There's no point talking about what happened with Celtic because the transfer window is now closed," said Dahan.
"Wisla wanted too much money for him. I'm not going to talk about amounts but, I can assure you, the bid from Celtic was well over £1m.
"Maor was disappointed with what happened, but he has to accept the decision of the club. He is a professional and if you sign a contract with a club you have to honour it.
"He must be a man and not act like a rabbit or a chicken. Since he has a contract with Wisla, he will play with them 100%. The truth is he didn't play at the weekend because of a back injury, not for any other reason.
"Wisla have financial problems which make it strange they didn't accept the offer from Celtic. So now we look for another club."