Potter, who was hired early this season and fired in less than a year, was consulted by the club's co-owners on the signing of the Benfica midfielder.
The Guardian now states that when Potter was asked by Todd Boehly and Behdad Eghbali about Fernandez, he believed the deal was too expensive.
He also felt the board was pursuing too many transfers in too short a period of time.
However, Eghbali was determined to sign Fernandez, leading the negotiations himself.
Potter felt he had a first team that was far too large for him to keep all the players fit and happy.