He has instead opted to continue his development in Catalonia and joins up with Xavi’s pre-season squad.
The Premier League trio were all offering significant financial incentives, but the teenager’s heart reportedly remained with Barcelona.
Southampton have had a relatively busy summer, bringing in five players who will likely battle for first-team spots.
Whilst a new centre-forward is still the main area of concern, allowing this deal to escape will remain a sore spot for Ralph Hasenhuttl and Saints supporters.
The Barcelona under-19s captain has earned huge praise for his calmness on the ball, and many have expectations of him reaching the levels of Pedri and Gavi. In fact, he is reportedly primed to be the natural successor to club legend Sergio Busquets.
Southampton have a brilliant track record of producing and developing young talent, so there seems little doubt that a move to the English south coast would have helped Casado develop further.
Remarked upon for his ability to beat the press with neat turns, break up the play and pick out a killer pass, the 18-year-old appears to have the qualities required to succeed in the Premier League.
He would have occupied Oriol Romeu’s current role commendably, and in time he could have succeeded the former Chelsea anchor man. Alongside the potent James Ward-Prowse, he could have been moulded into an all-round quality central midfielder at St Mary’s.
To combine the teachings of both of these midfielders could have helped Casado to fulfil the ‘next Busquets’ prophecy, as it would have been the perfect blend of brutality and brilliant technique.
Southampton supporters have every right to be gutted as a potential midfield star of the future instead opts to stick around in Catalonia.
The south coast club were always fighting a losing battle to pry him from one of the foremost football clubs in the world, but Hassenhuttl will likely still feel aggrieved that Casado will not be joining the Saints.