Atletico reportedly failed with an €18million bid for Edinson Cavani, whose contract at Paris Saint-Germain will expire at the end of the season, but there may still be new additions on deadline day.
"There are still a few hours left. Anything can happen," said Simeone.
The Atleti boss has been subject to increasing criticism in recent weeks, with his team falling 10 points behind LaLiga leaders Madrid and suffering elimination from the Copa del Rey to third-tier Cultural Leonesa.
Zinedine Zidane spoke out in support of his cross-city counterpart on Friday and Simeone was thankful for his words.
"It's nice when a colleague of Zidane's quality thinks this way. I return the message," said the Argentine.
"He is the ideal coach for Madrid. He has the rank and the ability to do what he feels. He returned to compete like he had before he left. Madrid have improved a lot defensively. They are very strong. They have many options in attack and that allows him to play with different players.
"It will be a match where the details and intelligence will have a lot of dominance."