Spain's Costa has hit 33 goals for Diego Simeone's side in a remarkable season for Atletico, where they have come out of the shadows of their more affluent neighbours Real Madrid and La Liga champions Barca.
They picked up a 1-1 draw in a typically hard-fought battle at the Camp Nou in the Champions League first leg last week, where Costa limped off with a hamstring strain in the first half.
His replacement Diego hit a stunning shot from distance to give Atletico a valuable away goal before Neymar grabbed a draw.
Costa has been receiving intensive treatment with the aim of being ready for the home leg and is progressing well. However, with further crucial games ahead, Atletico's medical staff are wary of him coming back too soon and aggravating the injury.
Arda Turan is also a doubt with a groin strain and if he does not recover then his place on the right wing would likely go to Diego with Adrian Lopez possibly replacing Costa.
Adrian came on as a substitute and looked lively during an otherwise tired Atletico display in a 1-0 home win over Villarreal on Saturday that kept them a point clear of Barca at the top of the Spanish championship.
"I am prepared, we are all ready for when we have to play. Any opportunity in this team is important and you have to be ready to take it," Adrian told reporters.
"It has been a great season so far and we are all pleased. We have done very well but we need to keep going game by game.
Now we are up against Barcelona in the Champions League and we will play it as though it were a final.
"The first leg was a good result but the tie is very open still. We know what Barcelona are capable of doing and we will have to have a great performance if we are going to qualify for the semi-finals. We will have to fight from start to finish."
Barcelona were also below their best but beat Real Betis 3-1 at the weekend with two more goals from Lionel Messi and remain on Atletico's shoulders with the two sides also still to meet at the Camp Nou in La Liga.
Their main injury concerns are at the back where Gerard Pique is missing with a hip injury so Marc Bartra could again deputise with Carles Puyol out long term.
Barca also have to finish the season with veteran goalkeeper Jose Manuel Pinto after Victor Valdes was ruled out with a knee ligament injury.
"It was a tough game (at the Calderon) where we put in a great effort and now for the return leg we will be in perfect condition," Pinto told Barca TV.
"It is likely to be a tight game, the same as the first, and small details will make the difference. We hope that these small details will go for us."
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