Brazilian midfielder Juninho has signed for Palmeiras in his native country after severing ties with Celtic.
Juninho scored just once for Celtic
The 32-year-old was released by the Parkhead club on Tuesday after an unhappy seven months at the club.
Juninho started just 14 games for Celtic - scoring once - as the form of young winger Aiden McGeady kept him out of the first-choice XI.
A club spokesman said on his departure: "Everyone at the club wishes him all the best for the future."
Celtic manager Martin O'Neill added: "It's been disappointing but I said to him I would not keep him a prisoner. He came to me a week or two ago and said he had an opportunity to go to Brazil.
"The league was starting up again and there was a possibility of him going so he asked if he could be freed from his contract and I didn't have a problem with it.
"Naturally I am disappointed. When we took over his contract from Middlesbrough he was finding it difficult.
"They were spending big money trying to improve their team and he was on the periphery of things.
"I thought he would come here and we would be a new lease of life for him and the response from everybody would be great.
"I thought his particular response would be just what we needed."
A World Cup winner in 2002, Juninho previously played for three other Brazilian clubs - Sao Paulo, Vasco de Gama and Flamengo.