3) Gianelli Imbula (Porto to Stoke – £18.3m)
A club-record signing for the Potters in the 2016 January transfer window, the Congolese midfielder failed to live up to expectations and was shipped out on loan after an eighteen-month spell.
Imbulla was a regular in his time with Toulouse and Rayo Vallecano, although a third temporary move to Lecce was ended prematurely. He left the Bet 365 Stadium on a free transfer to Russian club Sochi in March last year.
