28-year-old Diallo has featured for Rennes in the French top flight, as well as in the Europa League, and was part of the squad which lifted the French Cup in 2018-19.
He has picked up 17 caps for his national side, having also represented France at Under 19 and Under 20 level, and was part of the Senegal squads for the 2018 World Cup, as well as the 2017 and 2019 African Cup of Nations.
The shot-stopper started in the youth ranks of hometown team Reims before joining Rennes' youth academy, and made over 50 appearances on loan for Le Havre in the French second division, also playing for Turkish outfit Caykur Rizespor on loan.
Diallo now joins up with Sabri Lamouchi’s side to compete with Brice Samba and Jordan Smith for the goalkeeping jersey.