Barcelona faces a daunting task in their upcoming away match against Atletico Madrid, needing to overturn a 0-2 deficit. Defensive problems have emerged as a critical concern that could influence the outcome significantly.

Gerard Martín had to leave the pitch at halftime due to a right ankle issue, raising alarms amid other defensive absences. Flick opted to substitute him as a precaution but expressed hope Martín will be fit for the return leg, though his readiness remains uncertain.

Andreas Christensen remains sidelined with a long-term injury, and Pau Cubarsi is suspended, removing two key central defenders from the lineup. Should Martín be unavailable, the likely pairing would be Ronald Araújo and Eric García—both recently deployed in non-central defense roles: Araújo predominantly as right-back and García as a defensive midfielder.

This untested center-back partnership lacks the necessary cohesion and automatic understanding, posing risks against a high-caliber opponent like Atletico. Revisiting Koundé as a center-back is unlikely given that he hasn't played there for over a year. Another tactical possibility involves shifting García back to defense while pushing De Jong into midfield alongside Pedri, but Flick is unsure about De Jong’s match fitness for the full 90 minutes.

These factors highlight the importance of Flick's personnel and tactical choices ahead of the crucial second leg. The defensive setup will not only affect the back line's solidity but also the entire team's tactical balance. Fans should be aware that defensive stability is a pivotal factor in Barcelona’s pursuit of a semifinal berth.

In conclusion, Barcelona’s defensive shortage necessitates fresh tactical approaches from Flick and increased responsibility from the players. The team’s success or failure in this decisive Champions League match may hinge on how effectively their back line operates under these constraints.