Simeone unsure over Costa fitness
Costa, who has scored 33 goals in all competitions this season, strained his hamstring in the 1-1 first-leg draw at Camp Nou last week, and missed Saturday's 1-0 win over Villarreal in La Liga.
Simeone is hopeful that the 25-year-old will be available for Wednesday's second leg, but revealed that there is a contingency plan in place if he does not make it.
"We will have a look at Diego Costa in training later," he said.
"If he doesn't make it, Adrian Lopez will play. If Adrian plays I'm sure he will play a great game for us.
"We have rotated some players in the last few games which is important to keep the team fresh.
"We are doing a great physical work and that allows us to be competitive at this phase of the season."
Meanwhile, club captain Gabi advised caution over Costa, with Atletico also challenging for the league title along with Barca and fierce rivals Real Madrid.
"Diego is an ambitious player and I'm convinced that in his head he's definitely playing," he said.
"But we have to be cautious, and that the decision of whether or not he plays tomorrow could be decisive for the rest of the season, so he has to be fit.
"He'll try his best to be, but he will be as he is. The boss will decide. He's vital like Leo Messi is for Barca, he's a decisive player for us.
"But if he can't play we will still give our all and it will be harder, but we will try and win."