According to Marca, Grimaldo's defending has been questioned, and Hancko could play at left-back against Liverpool.

Grimaldo's problems in closing down his side have once again highlighted the long-standing unresolved issues at left-back. Galan was previously exposed by Liverpool in a two-minute spell a year ago.
It would not be accurate to blame Atletico Madrid's defeat at San Mames entirely on Grimaldo, but it cannot be denied that Simeone continues to face the same old problems at left-back. Moreover, Atletico are about to visit Anfield, where Galan suffered a heavy blow from Salah a year ago, conceding two goals between the fourth and sixth minutes. Athletic Bilbao's lapse also lasted the same two minutes, with the Spain international appearing in the footage as almost the player in the most disadvantageous position. It appears that Liverpool have already sounded the red alert.
When Grimaldo arrived at the Metropolitano, he carried the aura of a World Cup champion. Although Cucurella kept him on the bench and he barely received playing time, he had once been Atletico's top target, but after Real Madrid intervened, Atletico turned to an alternative option. Added to his 'striker-level' statistics at Leverkusen — 30 goals and 45 assists in 145 appearances — his first few matches after joining have still left questions over his defensive performances.
Besides being beaten by Roberto Navarro at San Mames, who easily scored to make it 2-0, and failing to protect his area in the 1-0 goal, forcing Hancko to cover for Inaki Williams, Grimaldo also allowed Miguel Sierra to take a comfortable shot from his side in Sevilla's goal in the previous round. These are clear signals that Simeone needs to solve a long-standing problem.
More accurately, this issue has existed since Filipe and Lucas Hernandez left in 2019, because none of their successors have truly filled the gap. Rodi, Galan and Ruggeri have all been affected by defensive shortcomings, although Ruggeri performed reasonably well in some duels against Yamal; meanwhile, Reinildo was solid like a wall but suffered because of his limited attacking contribution.
In fact, even Reguilon failed to fix this weakness. Simeone later relied on temporary solutions more than once, such as moving Saul into this position, shifting Hermoso to the flank, or directly using a wing-back like Carrasco. These emergency options are now alternatives again for the trip to Anfield.
Hancko has become the leading candidate.
In this situation, the possibility of Hancko playing left-back against Liverpool is increasing. On one hand, this is intended to close down the flank, as Victor Munoz or Barcola could create threats from that side; on the other hand, Castro-Romero is close to becoming a defensive leader, and Atletico hope he can restore the defensive solidity of previous years, when Filipe or Lucas provided reliability on the flank. Admittedly, this is not the Slovak player's most natural position, but with a lack of specialist options — which also explains why Atletico negotiated with Tagliafico until the final day of the transfer window in an attempt to agree all the figures — Hancko appears to be the best choice for restoring order.