Celtic have confirmed winger Aiden McGeady has joined Spartak Moscow from Celtic on a four-year contract.
Republic of Ireland international McGeady had been linked with a move to England, but will now head to eastern Europe in a deal believed to be close to £10 million.
McGeady told Celtic's official website: "I would like to take this opportunity to thank everyone at Celtic Football Club for making my time here so enjoyable and memorable. The Celtic fans are second to none and it is a fantastic club to play for."
He added: "Celtic is the team I have supported my whole life and will miss so many things, however I am looking forward to the challenge of playing for Spartak Moscow.
"I wish the current players and management all the very best for the season ahead and I will be back whenever I can to cheer the team on."
Hoops boss Neil Lennon said: "I would like to wish Aiden all the best with his move to Spartak Moscow. It is obviously a disappointment to lose a player with Aiden's talent. However, it was his desire to try and further his career in pastures new and I respect his decision.
"Spartak Moscow are a good club and I am sure Aiden will do very well there. I would like to wish Aiden and his family the very best of luck for the future."
Paddy McCourt has said he is hoping to fill the void at Parkhead.
"We have probably lost our best player in the league so he is going to leave a big hole but it's up to someone to step up to the plate and fill it," he said.
Asked whether that person could be him, he replied: "I think so, me and maybe a couple of other boys. It's up to whoever gets the shout against Inverness tomorrow (Saturday).
"They've got the jersey and it's up to them to hold onto it and I'm hoping it will be me. It's very important - it's the most important season since I've been here to be honest.
"The first one I found tough and I struggled a lot. Last year I was quite happy with the games when I did come in and play. This is the year where I really want to kick on and be a regular in the side."