Rumours emerged in November claiming that Mascherano had been 'offered' to former club Liverpool, possibly as a gesture of good will to grease the wheels in the ongoing Philippe Coutinho saga.
Barça have also been heavily linked with Colombian defender Yerry Mina, more so in light of Umtiti's enforced absence, but Valverde has now stressed Mascherano's continued importance.
"The transfer window hasn't arrived yet. We've been talking about the winter transfer window since August. When it comes we will talk about the winter transfer window," Valverde told gathered reporters ahead of this week's Champions League fixture.
"We are still counting on Mascherano. He is a member of the team, is committed to Barcelona and has been for a long, long time.
"I can't talk about hypothetical conversations really. I'm happy with Mascherano. I want him to be here with us. I've not got concern about him."
Mascherano himself has been nursing a hamstring injury in recent weeks after playing for Argentina on international duty. He had been tipped to pursue a transfer to ensure he remains a part of the national team squad ahead of the World Cup, but he may now have a renewed opportunity at Barça.