Marlon was loaned out to Nice on a two-year deal last summer, which included the option for the Ligue 1 side to make the transfer permanent if the 22-year-old impressed at the Allianz Riviera.
However, the deal will not be made permanent as Nice announced two weeks ago that Marlon would return to Barcelona for the 2018/19 season.
Previous reports claimed that West Ham were interested in the young Brazilian but would only pay €15m, significantly short of the €25m demanded by Barcelona.
Mundo Deportivo has claimed that another Premier League club is interested in Marlon, but the Hammers are believed to be in 'pole position' to make their fourth major signing of the summer transfer window.
Barcelona are finalising the transfer of Marlon Santos to West Ham. There is already an agreement in place for the Brazilian centre-back to move to the Premier League club for £13.3m. Agent Kia Joorabchian has been key in trying to finalise the deal.— West Ham Central (@WestHam_Central) June 29, 2018
Today's edition of Mundo Deportivo claims that Barcelona have made plans to sanction the sales of several players who are deemed surplus to requirements at the Nou Camp, and Marlon is one player mentioned as being on their list.
With the new football financial year beginning on the first day of July, it is common practice for clubs to wait until this date before agreeing to sell players, so we may know within the next few days whether West Ham's interest will come to fruition.
Despite the rumours of another interested Premier League club, West Ham is the only team named in the report, which would seem to suggest that if Marlon does leave then the London Stadium will be his destination.