Marvin Compper was conspicuous by his absence as Celtic sent their best wishes to a series of departing players.
German defender Compper left for Duisburg last week after making one first-team appearance during an 18-month stay in Glasgow.
But he was left out of a list of 19 first-team and reserve players who were wished well for the future in a story on Celtic's official website.
It read: "Dorus De Vries has announced his retirement from football, having spent three years at the Scottish champions. During his time at Paradise, the 38-year-old goalkeeper won three league titles, three Scottish Cups and three League Cups, and will now continue to pursue his coaching badges in the Netherlands.
"Celtic Football Club wishes Dorus all the very best in his future endeavours, and extends the same gratitude to departing players Emilio Izaguirre, Cristian Gamboa, Regan Hendry, Dedryck Boyata, Mikael Lustig, Filip Benkovic, Scott Allan, Youssouf Mulumbu, Oliver Burke and Jeremy Toljan.
"Likewise, the club wishes every success to its outgoing reserve players Reece Willison, Ross McLaughlin, Wallace Duffy, Thomas Caffrey, Lewis Bell, Ciaran Diver, PJ Crossan and Kristi Marku.
"The club also welcomes back its returning loan players, Ross Doohan, Jack Aitchison and Robbie Deas."
Compper's exit was marked by a single tweet on the club's official Twitter account on Tuesday, which read: "#CelticFC can announce that Marvin Compper has left the club by mutual agreement following the termination of his contract."
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