Liverpool swooped for the former Porto star midway through last season and the Colombia international hasn't looked back since. Diaz won the League Cup and FA Cup last season, while also helping the Reds to being runners up in the Champions League and Premier League.
Local reporter Gerard Romero states Barcelona missed out on the chance to sign L Diaz during the January transfer window due to Financial Fair Play rules.
The La Liga giants' current issues as a club are well-documented, having handed out lucrative contracts to players in recent years and paying extortionate transfer fees.
Diaz would sign for the Reds in the end and Barcelona recruited Ferran Torres from Manchester City, though Romero has claimed the Spanish side could have signed the Reds' Colombian star were it not in such a poor financial situation.