The former Barcelona striker is his side’s top scorer this season with nine goals across all competitions including eight in his last nine appearances.
He is said to be feeling muscular discomfort at the moment and trained alone on Friday rather than with his teammates, as he attempted to reach a level of fitness to be ready for the encounter.
Alcacer partners Gerard Moreno up front for Unai Emery’s side and his absence would be a significant blow for the encounter against the Spanish champions.
It is unclear how the Yellow Submarine would reorganise their attack in his absence, with it suggested that Carlos Bacca may come in as a direct replacement.
There is also the options of playing Samuel Chukwueze or Takefusa Kubo instead and pushing Moreno into a more advanced role.
Image via Diario AS