Mascherano has constantly hinted in recent weeks that his Camp Nou career is coming to an end, despite being under contract until the summer of 2019.
A move to his Argentine homeland or Major League Soccer has been touted, but an untimely injury picked up by Samuel Umtiti last weekend - keeping him out of action for the next two months - means that Mascherano will now likely be required until the end of the campaign.
Despite his side's growing injury woes, however, Valverde claims that he will not rush into making new signings next month.
"The transfer window hasn't arrived yet. We've been talking about the winter transfer window since August," he told reporters. "When it comes we will talk about the winter transfer window.
"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.
"We've got December to think about these things but Samuel Umtiti's injury is not a long-term one. By January, he should be coming back. We have some injury problems that we have to think about but we have more analysis to do in that [transfer] department before I can make any official statement."
Mascherano has featured 10 times for Barcelona in all competitions this term, most recently in the 2-1 win against Sevilla on November 4.