“I thought they were looking at offsides, but then I saw it on the video board, and I think it was a handball,” Barcelona coach Xavi said.
Williams laughed at the decision on Twitter after the game.
“We are upset,” Bilbao coach Ernesto Valverde said. “Nobody on the field had seen anything, not even the referee or the fourth official or the other assistants.”
The review of Williams’ goal took nearly three minutes. When the decision was announced, it drew loud jeers from the home fans at San Mamés Stadium.
Madrid had moved to six points off the lead with a 3-1 win at Espanyol at home on Saturday. Barcelona and Madrid play the final league “clasico” next week at Camp Nou stadium.
The controversy came hours after Madrid had announced it would side against Barcelona in the legal proceedings that the rival is facing over its payments of millions of euros over several years to a company that belonged to the former vice president of Spain’s soccer refereeing committee.
Prosecutors on Friday formally accused Barcelona of alleged corruption in sports, fraudulent management and falsification of mercantile documentation. An investigating judge will decide whether the accusations should lead to charges. The Catalan club has denied wrongdoing.
Xavi said the team has not been talking about what may happen because of the legal proceedings.
“We are focused on playing soccer,” he said. “People are reaching conclusions ahead of time. It’s sad.”
Raphinha scored the winner in first-half stoppage time with a shot from inside the area after a superb pass by Sergio Busquets. The lineman raised his flag but video review determined the Brazil forward was in a legal position.
There didn’t immediately appear to be anything wrong with the goal by Williams, but the referee was asked to look at Iker Muniain’s touch of the ball with his arm earlier in the buildup, and it was deemed to have been enough to disallow the goal.
Bilbao, which stayed in ninth place, hit the woodwork a couple of times and was also stopped by great saves from Barcelona goalkeeper Marc-André ter Stegen.
Bilbao has not won any of its last seven games against Barcelona in the league, with one draw and six losses since a 1-0 victory in 2009. The Basque Country club has not scored in its last three games against the Catalan club in the competition.
Robert Lewandowski returned for Barcelona after the striker missed a couple of matches because of an injury.
Real Betis and Villarreal dropped points in their bid for Champions League places after a 1-1 draw.
Borja Iglesias opened the scoring for Betis in the 38th minute and the hosts equalized through Yéremy Pino in the 55th.
The result kept Betis in fifth place, three points behind Real Sociedad in the final qualification spot for the Champions League. Villarreal stayed sixth, four points behind Betis.
It was the second league draw in a row for Betis after three straight victories. Villarreal had won two consecutive games in the league.
Third-place Atletico Madrid, level on points with Sociedad, visits midtable Girona on Monday.
Carlos Fernández scored three minutes into the match but fourth-place Sociedad couldn’t manage more than a 1-1 draw at Mallorca to see its winless streak reach five consecutive matches.
Sociedad has only one win — at Espanyol in the league in February — in its last nine matches in all competitions. It has four draws and four defeats during that run.
South Korea midfielder Lee Kang-in equalized early in the second half for 10th-place Mallorca, which is winless in three consecutive games.
Sevilla came from behind to beat Almeria 2-1 at home with goals from Lucas Ocampos in the first half and Erik Lamela in the second.
It was the second win in a row after three consecutive losses in all competitions for Sevilla, which moved to 13th place, two points clear of the relegation zone.
It was the fifth loss in six matches for Almeria, which opened the scoring with Sergio Akieme in the second minute.
Almeria dropped to second-to-last-place.
Tales Azzoni on Twitter: http://twitter.com/tazzoni
More AP soccer: https://apnews.com/hub/soccer and https://twitter.com/AP_Sports