AC Milan chief exec Giorgio Furlani says more signings could happen this month.
Filippo Terracciano has arrived from Hellas Verona and Mattia Gabbia has been recalled from his loan with Villarreal.
Furlani told Sky Italia: "It's nice to be in the race all the way, we would have preferred to still be in the Champions League, in the Italian Cup and be better positioned in the league.
"Tonight (against Atalanta) the episodes weighed heavily. Reinforcements on the market? The market has been open for 10 days, we have signed two players in defence: Gabbia and Terracciano.
"We are always open to opportunities, if there are opportunities we will seize them."