Goalkeeper Jan Oblak may return to the starting lineup after being sidelined for over a month due to a muscle injury.

Atletico will host Barcelona on Tuesday, hoping to capitalize on their 2-0 victory from the first leg in Barcelona last week. Coach Diego Simeone mentioned on Monday that Oblak’s return is a possibility, even though he hasn't played since the team’s 5-2 win over Tottenham in the round of 16 on March 10. Oblak has been training with the squad recently and is reportedly fit to start.

"I still haven't told the players who will start," Simeone stated, adding that he would likely wait until closer to game time for any announcements regarding the lineup.

Oblak suffered his injury during the match against Tottenham. Since then, Argentina’s Juan Musso has filled in as goalkeeper, conceding 10 goals in six matches, including two in Atletico's recent 2-1 loss to Sevilla in the Spanish league.

The starting goalkeeper will face a formidable Barcelona attack featuring Lamine Yamal, Ferran Torres, Robert Lewandowski, and Marcus Rashford. However, Barcelona will be without Raphinha, who is sidelined with a hamstring injury.

This matchup marks the fifth encounter between Atletico and Barcelona in less than two months. Barcelona previously won 2-1 in Madrid during a league match on April 4. The teams also faced off twice in the Copa del Rey semifinals, where Atletico triumphed 4-0 at home but advanced to the final despite a 3-0 loss in the second leg in Barcelona.

Atletico will enjoy home-field advantage in the second leg, with nearly 70,000 fans expected at the Metropolitano Stadium. Around 3,000 Barcelona supporters are also set to travel to the Spanish capital.

"We are convinced of what we need, and we'll play the game we need to in order to advance," Simeone said. "We know the quality of our opponent, but we are focused on our objective, which is to progress."

Atletico was eliminated by city rivals Real Madrid in the semifinals during the 2016-17 season. They have also lost two finals to Real Madrid in 2014 and 2016 and have yet to win the Champions League.

Barcelona, a five-time European champion, reached the Champions League semifinals last year but was eliminated by eventual runner-up Inter Milan.

The team that advances on Tuesday will face either Arsenal or Sporting Lisbon in the semifinals. Arsenal won the first leg 1-0 in Lisbon last week, with the second leg scheduled in England on Wednesday.