#4 Guido Carrillo
Monaco - Southampton
Date of arrival - 24 January 2018
Transfer fee - £19.2m
Southampton received a world record fee of £75m when they sold Virgil Van Dijk to Liverpool in January 2018 and as such had excess cash to burn and like most other clubs who found themselves in similar positions, The Saints splashed the cash on a player who proved to not be worth it.
The player in question happens to be Argentine forward Guido Carillo who had been an unspectacular backup to Falcao and Mbappe during Monaco's record-breaking 2017 season but was still relatively unknown which made the decision by Southampton to spend £19.2m on him really baffling.
Carillo had zero impact at the St Mary's, making just seven league appearances without a goal, before being shipped out on loan less than six months after arriving (a recurring theme in this piece) to team up with the man who sanctioned his purchase (Maurizio Pellegrino) at Leganes in Spain.