Correa came on in the 86th minute but was left in pain following a strong challenge in stoppage time from midfielder Jude Bellingham, who was booked.
"Angel Correa sustained a grade 1 sprain of the medial collateral ligament of the knee," Atletico said in a statement. "The Argentina international has undergone an MRI scan that has confirmed the injury."
Spanish media said Correa could be sidelined until after the international break in mid-October.
Correa's absence is another blow for Diego Simeone's side who are already without the injured Thomas Lemar, Reinildo Mandava, Caglar Soyuncu, Pablo Barrios and Rodrigo De Paul.
