Question: Which Argentine professional footballer who plays as a defensive midfielder or centre-back for Spanish club FC Barcelona and the Argentina national team was contracted under Alberto Dualib?
Sentence (from "Javier Mascherano"): Javier Alejandro Mascherano (] , ] ; born 8 June 1984) is an Argentine professional footballer who plays as a defensive midfielder or centre-back for Spanish club FC Barcelona and the Argentina national team.
Relevant evidence: Yes