Barcelona's Robert Lewandowski attempts a shot at goal during the Champions League Group H soccer match between Barcelona and Royal Antwerp at the Olympic Stadium of Montjuic in Barcelona, Spain, on Sept 19, 2023. (PHOTO / AP)

MADRID - It promises to be a tense fifth round of games for FC Barcelona and Atletico Madrid in the Champions League on Tuesday as their future in the tournament is on the line.

Although both sides lead their respective groups, a defeat for Barca at home to Porto would put its place in the last 16 under threat, while a defeat for Atletico away to Feyenoord could see it drop to third in the group and leave it facing another early exit from the tournament.

Barcelona coach Xavi Hernandez is still sweating over the fitness of goalkeeper Marc-Andre Ter Stegen, who missed Saturday's 1-1 draw away to Rayo Vallecano with a back problem, with Inaki Pena stepping in to replace him.

Ilkay Gundogan, Joao Felix, Jules Kounde and Ronald Araujo are all likely to start after Xavi preferred to have them on the bench at the weekend to avoid injury after a busy international schedule.

ALSO READ: Atletico fight back to draw thriller with Celtic

Atletico Madrid's Spanish defender #22 Mario Hermoso and Celtic's Irish defender #05 Liam Scales fight for the ball during the UEFA Champions League group E football match between Celtic and Atletico Madrid at Celtic Park stadium in Glasgow, Scotland, on Oct 25, 2023. (PHOTO / AFP)

The Barca coach needs to see his side pick up their form after recent poor displays, with the team developing a worrying trend of playing poorly in the first 45 minutes, before improving after the break.

"We have to win if we want to get into the next round. Porto is a difficult rival, but I think we will be able to get the result," commented Pedri after Saturday's game.

Although a win away to Feyenoord would see Atletico into the last 16, they are in a more delicate position than Barcelona, because defeat would see their rivals leapfrog them in the group, while second-place Lazio is the clear favorite to win their home game against Celtic.

With Lazio due to travel to Madrid in the final group game, Diego Simeone needs to avoid defeat on Tuesday night at least, otherwise, his side would need to beat the Italians in order to book a place in the last 16.

READ MORE: Barca below par again as Rayo hold them in Vallecas

Simeone fielded a strong side in Saturday's narrow win at home to Mallorca, although Rodrigo de Paul and Nahuel Molina could come into the starting 11 in the Netherlands, with Manuel Llorente pushing into an advanced role instead of Angel Correa.