Attacking midfielder Bernard Sun joined Blues on a two-year contract on 2 September 2019.
In doing so he created history by becoming the first Chinese-born player to join the Club.
A free agent since leaving Spanish side Estudiantes de Murcia in the summer of 2019, Sun came over to Blues to train with the Under-23s and appeared as a substitute in a pre-season friendly against Olympiacos.
Sun was born in Beijing and moved with his family to Koblenz in Germany when he was seven.
He came through the youth ranks initially with Kaiserlautern before moving to Eisbachtal.
From there the China Under-18 international went to Spain and Jumilla and played for their second-string outfit, Estudiantes de Murcia.
He was loaned to Segunda Division side Gimnastic de Tarragona in January and has been attracting interest from the Chinese Super League.
Sun, who holds a German passport, can play either up front or in midfield.