The 20-year-old attacker arrived from Benfica in a €126million deal at the start of the season and has scored five goals across all competitions.
"Everyone can see what is expected of Joao, he's a young boy and he has lots of room for improvement," Koke said post-match.
"Many great players have had to adapt to Atletico and it's not easy, he's young.
"If he listens to the boss and his team-mates, he will be the player that everyone wants to see.
"He's not been lucky with injuries, but I'm sure that, in the future, we'll see the Joao we want to see."
Atletico came from behind in the Spanish capital, where Simeone's side trailed to Paco Alcacer's 16th-minute opener at Wanda Metropolitano.
"Speaking about Koke, our captain, our talisman and one of our longest-serving players [with] Saul [Niguez], [Jose] Gimenez, Thomas [Partey]," Simeone said.
"He knows what we're looking for, a tactical condition that lots of players don't have and a pass that seems slow but he knows where he is.
"He can play on the right, in the middle. He and Saul are the ones who can play in any position."
Simeone paired Correa with Alvaro Morata up front and the Atletico head coach added: "The two worked very well, they have lots of strength in their feet to go out and press people. Morata did a very good job and Correa is in fantastic form. We're very happy with the competition for places.
"The return of [Kieran] Trippier, Joao Felix... [Yannick] Carrasco is getting better, [Sime Vrsaljko] is very strong, Vitolo had a great game and the substitutes brought fresh legs."