Last week, Kayserispor agreed terms with Spanish giants Atletico Madrid to sign the Ghana midfielder on permanent basis.
Mensah spent the 2018/19 season on loan with the Anatolian Star and impressed.
This prompted the club to agree a three-year deal with the 24-year-old.
Mensah who missed out in the Black Stars provisional squad for the Africa Cup of Nations scored three goals in 21 appearances for Kayserispor last season.
He joined Atletico Madrid from Getafe prior to the start of the 2016/17 season but failed to break into the squad which saw him return to his former Club Vitória Guimarães on loan before extending his loan spell to Turkish Club Kasimpasa. Read Full Story