Athletic Bilbao boss Ernesto Valverde has bemoaned the referee's decision not to award his team a penalty in Sunday's Basque derby at Real Sociedad.

The visitors appeared to have a strong shout for a spot kick in the first period when Asier Illarramendi seemed to handle an Aritz Aduriz shot inside the Sociedad box.

Valverde has claimed that the incident could have been "decisive", but has admitted that his team were once again far from their best.

"Our performance in the second half was not as good as our one in the first. Still, the penalty [which ultimately wasn't given their way] could have changed the match and been decisive," Valverde told reporters.

"Real asked a lot of us because they pressed well. We needed to take a step forward for the win and tried to be in control from the start."

Bilbao have only won one of their first six league games this season.