Alaves edged out Eibar in Sunday’s Basque derby thanks to an early strike from striker John Guidetti on the day of his 26th birthday.
The Swedish international found the net with his fifth minute strike from outside the area in what proved to be his side’s only shot at goal.
The hosts dominated the chances – racking up 15 shots – and enjoyed the lion’s share of possession but could not force their way back into proceedings.
The result all but ends Eibar’s European hopes as Jose Mendilibar’s side slip to 12th in the standings while Alaves climb to 15th.
