Zheng Zhi will not be able to play in Celtic's Europa League group games after UEFA confirmed he was not registered in time.
The Hoops were trying to wrap up the free transfer of China captain Zheng on Wednesday after he arrived in Glasgow on Tuesday evening to pen a reported two-year deal.
Although the 29-year-old is able to complete a move outside the transfer window, Celtic needed to register the player with the Scottish Football Association by 11pm on Tuesday night for him to be eligible for European competition before the new year.
UEFA revealed on Wednesday afternoon that this had not happened, meaning Zheng - who is able to play in both midfield and attack - will be forced to sit out the Hoops' European campaign until the knockout round begins in February.
A work permit was the main stumbling block to the completion of the transfer of Zheng, who is a free agent after being released by Charlton.
Manager Tony Mowbray remained behind in Glasgow to conclude the deal on Tuesday night, while assistant Mark Venus took Celtic - minus their international players - to Toronto for a friendly against Benfica.
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