Southampton fullback Cedric Soares is being linked with Barcelona.
El Mundo Deportivo says Barcelona's sporting director Robert Fernandez scouted three players during Portugal's 7-0 defeat of Estonia on Wednesday.
Barca are bracing themselves for a busy summer of transfer activity, with the La Liga champions considering bringing in a right-back, a back-up forward, a centre-back, a left-back and a central midfielder.
Fernandez travelled to Lisbon earlier this week and monitored the displays of Southampton fullback Soares, Lorient left-back Raphael Guerreiro and Valencia midfielder Andre Gomes, 22.
Gomes is also a target for Manchester United and Juventus.