Mundo Deportivo explains the club are following some players in this position
Barcelona have 5 centre-backs in their current squad: Piqué, Mascherano, Mathieu, Vermaelen and Bartra. However, according to Mundo Deportivo, the club is not satisfied with the performances of Mathieu and Mascherano, Luis Enrique doesn't trust in Bartra and Vermaelen is injured again. So Robert Fernández is following some of the best centre-backs around Europe to try to strengthen the team in the forthcoming transfer windows.
Mundo Deportivo puts four names on top of the table in today's edition: Laporte (Athletic Club), Marquinhos (PSG), John Stones (Everton) and José Maria Giménez (Atlètic de Madrid). All four big names for their respective teams so Barcelona will need to pay a lot of money if they want to secure their signing.