Injuries and the form of Luis Suarez have limited the former Valencia man's game time so far this season, but with the Uruguayan suspended for the visit of the Basques, Alcacer took advantage.
With just eight minutes gone, Jordi Alba was played in down the left, with his low pull-back perfect for Alcacer to slide the ball past Kepa Arrizabalaga and into the far corner from the penalty spot.
The goal did prove to be a controversial one though, with replays showing that Alba was offside when he received the ball in the build-up.
Check out the strike for yourself below:
18 de marzo de 2018