Nico struck on the night as Athletic secured a place in the top eight after the group phase.
He said afterwards: “We are tied with the leader, that is easy to say. We have to continue with this mentality, working every day to improve. I think that if we continue prioritising the collective over the individual, as we always do, success will come.
“We knew it was going to be a difficult match, but with this atmosphere at San Mamés, who wouldn't get the three points here?"
Brother Inaki Williams created the goal for Nico on the night.
He added, “My brother has been insisting a lot that I should come in front, and today he has given me another little piece of candy. I am very happy for him and for me. We want to continue growing and helping the team with goals and assists."