Celtic have confirmed that defender Andreas Hinkel has been ruled out for nine months with an anterior cruciate ligament injury.
The German right-back picked up the injury at training on Tuesday and will have to undergo an operation.
A statement on Celtic's official website read: "It is with great regret that Celtic Football Club announces that, after an accident in training, Andreas Hinkel has suffered significant injury to his right knee."
The statement continued: "It has been confirmed after MRI scans as a rupture of the anterior cruciate ligament.
"Andreas will be referred for the appropriate investigation and assessment. He will require surgery and could be out for a period of up to nine months.
"Clearly this is very sad news for Andreas and he will be receiving every support from the club."
Hinkel was not included in Neil Lennon's Europa League squad and would not have played against FC Utrecht in the first leg of their play-off on Thursday at Parkhead.
The Hoops boss had indicated during the summer that recent signing Cha Du-Ri was his first choice right back.
Hinkel, who joined Celtic in January 2008 from Spanish side Sevilla, is one of the higher earners at Parkhead and in the final year of his contract.
The former Stuttgart player was expected to be sold to free up money to allow Lennon to further refurbish his squad.
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