Shaun Maloney has confessed he should never have left Celtic for Aston Villa after rejoining the Scottish champions on a four-year deal worth up to £2.5m.
He passed a medical at Celtic Park on Thursday to seal his return to the Scottish Premier League champions.
"I shouldn't have come to a situation to leave Celtic," Maloney said.
"I knew it was not the right move and I really struggled - in my heart of hearts I knew Villa was not the club I wanted to play for."
Maloney has been persistently linked with a return to Celtic since his switch to Villa Park in January 2007.
Last week, the 25-year-old's agent John Halliwell claimed that three clubs had expressed an interest in the unsettled Scotland international.
Malaysian-born Maloney, who made his Celtic debut in April 2001, left for a £1m fee after failing to agree new terms at Parkhead.
He failed to establish himself as a first-team regular at Villa but will also face strong competition for a place at Celtic.
Indeed, Celtic manager Gordon Strachan stressed that he had thought long and hard about the benefit of bringing the player back from Villa.
"A lot of players would love to come back to Celtic, but I would not bring them back unless I knew they would improve the team," he said.
However, Celtic midfielder Paul Hartley believes added strength in depth can only be good for the club.
"I played with Shaun at international level and I know what he can bring to the team," said Hartley.
"We have five or six Scottish internationals in the Celtic team already, so he will be another good addition.
MY SPORT: DEBATE"We have a good squad as it is now and we know Shaun can play in a number of positions.
"He had a good spell at Celtic the first time, so I'm sure he will do well again."
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