Costa has been in prolific form for Diego Simeone's men this season, firing the side to the top of La Liga as well as a Champions League final date with city rivals Real Madrid.
Goal revealed on Friday that the Brazil-born Spaniard has agreed a £35 million move to Stamford Bridge this summer, but Cerezo insists there have been no official developments.
"It's not the time to talk about signings," he told the Spanish media. "There are three very important games ahead.
"Diego Costa was signed when he was 18, almost a child, and nobody guessed what he would be today.
"Chelsea? We don't want to know when these games are so important. We don't want to destabilise the team and we can talk about this later.
"I can say that there is nothing, not officially, from another club to one of our players. They're not on their way to another team.
"If the question is 'is there a deal for Costa' then we haven't heard anything."