BARCELONA defender Gerard Pique slammed the referee after his side's 2-1 loss to Athletic Bilbao in the Copa del Rey.

First-half goals from Aritz Aduriz and Inaki Williams saw Bilbao, who would finish with nine men, claim their win at home in the last-16 first leg.

But Barca were denied a penalty to Neymar, while Aduriz was perhaps fortunate not to be sent off by referee Fernandez Borbalan.

Pique was furious and felt his team were perhaps denied two spot-kicks at San Mames on Thursday.

"I think it's a clear penalty [on Neymar]," he said, via Mundo Deportivo.

"I think mine with the goalkeeper is another penalty, but we know how this works."

Calling on improvement from referees, Pique added: "We want to play football and not roulette."

A second-half Lionel Messi goal leaves Barca in a decent position ahead of the second leg at Camp Nou on Wednesday.

Pique is confident his team can still advance to the quarter-finals, saying: "The result is a result which leaves the tie wide open so let's see.

"I hope it will be a great occasion at Camp Nou."