The La Liga giants are currently prevented from registering new players under the restrictions of a transfer ban.
They have, however, put in a deal in place for Sevilla winger Vitolo, with his €36 million release clause triggered and a short-term loan at Las Palmas sanctioned.
He could be joined by another fresh face at Atletico in the New Year, with the club hoping to reach another agreement before the window of opportunity slams shut.
Chief executive Miguel Angel Gil Martin told the club’s official website: “The ban of registering players this summer market affects us in that the two players that we wanted to hire, because there were only two, will have to join us with five months of delay.
“I always said that the decision to hire Diego [Simeone] and his decision to accept has been a great success for both sides.
“It is a clear example of successful synergy, where both parts have grown equally. I am sure that we have ahead several more years of joint work, where we can all continue growing."
Atletico have been heavily linked with a move to bring unsettled Costa back to Spain from Premier League champions Chelsea.
Despite delivering a steady stream of goals throughout three seasons in England, the Spain international has grown unsettled at Stamford Bridge.
He has been informed that he no longer figures in Antonio Conte’s plans and has fuelled the Atletico return rumours with his antics on social media.
Costa is, however, a much sought-after figure – having shown himself to be one of Europe’s top strikers – and ambitious Serie A outfit AC Milan are also monitoring his situation.