Rumours have been swirling that the 22-year-old will be recalled from his season-long loan spell by the Spanish giants when the transfer window reopens in January.
Despite injuries to senior centre-halves Willy Boly and Ryan Bennett, Vallejo has not featured since the 1-1 draw with Southampton in October. But Nuno stressed he still has time.
He said: “When the moment comes to have a decision then we will naturally have it.
“It has to involve all of the parties – us, Jesus and his club Real Madrid.
“We have to sit down and figure out what is best for all of us. We still have the month of December, he is still totally involved in the group, working well.
“He is not having his chance, but he is a player that is still with us.
“We don’t give up on players – ever.Every player that is here, we try to improve them.”
One player who has developed since his arrival at Molineux is Adama Traore. The 23-year-old has been in electric form on the right of Nuno’s front three.
But the Portuguese boss says with just three goals this term, he still has room for improvement.
He said: “There is still a lot of things for Adama to do to improve – goals.”
And Nuno explained that patience is key when it comes to improvement, but urged his players not to stand still as they head to Brighton tomorrow.
He said: “Some players take longer, some players don’t and can express themselves sooner in the team. You need patience to go alongside the players is the best way to improve them.
“If he doesn’t give you a fantastic answer or fantastic performance in one game or during a period, you cannot give up.
“Let’s try to figure out what is going on and what can I do to make him better and transform him into a good player to be a solution for us?
“That is why we never abandon a player, not even in one training session.
“It has to be this way.
“It is a never-ending process though because the game is so dynamic.
“That is why you can be doing one thing now which is working out but you have to be prepared for what is coming up next because suddenly you can do the same thing and it may not work out.”