Mascherano has started only six La Liga games so far this season, with Thomas Vermaelen typically selected by Valverde as Gerard Pique's partner in the absence of the injured Samuel Umtiti.
Barcelona have signed Yery Mina from Brazilian club Palmeiras for €11.8 million. The 23-year-old Colombian has signed a five-and-a-half-year contract with the Catalans.
"Yerry Mina now comes to Barca with the opportunity to continue developing as a footballer following his move to Europe. Without a doubt the Colombian has the potential to make it," the club said in a statement.
The Colombia international will strengthen Barcelona's defensive options as Javier Mascherano is reportedly expected to leave Camp Nou in the January transfer window, with Chinese Super League side Hebei China Fortune reportedly keen on the experienced Argentine.