Spanish news outlet Sport claims that Marlon, 22, has opted to join the Saints over the Hammers this summer, and the deal worth £10.6million is understood to be close to being wrapped up within the coming days.
It is a blow for West Ham to miss out on the Brazilian centre-back, but they must bounce back, and to do that they must complete the signing of Fabian Balbuena from Corinthians as soon as possible.
It is clear that Manuel Pellegrini has made bolstering his defence a priority this summer after he was appointed to replace David Moyes in charge of West Ham.
Issa Diop and Ryan Fredericks have already been signed up by the club, but he must top off this defensive overhaul by signing Balbuena, who has been in top form in South American for Corinthians.
The Paraguay international has captained his club in the Copa Libertadores and has won the Brazilian top-flight title.
The 6ft 2 (transfermarkt) enforcer is already on the Hammers’ radar as well with the Times reporting that he is edging close to a move to the London Stadium this summer.
Pellegrini will clearly know all there is to know about his fellow South American and the defensive ace should be snapped up now, as a perfect way to bounce back from the disappointment over Marlon.