The 28-year-old Spanish striker, who filled the void left by the departure of talisman Inaki Williams for the Africa Cup of Nations with Ghana, had a decisive effect as Athletic edged Spanish champions Barcelona on goal difference.
The fourth-placed Catalans are in Saudi Arabia for Sunday’s Spanish Super Cup final against league leaders Real Madrid.
Real Sociedad scored a late goal through Mikel Oyarzabal, but could not find the equalizer at the colorful San Mamés.
Athletic are hoping to finish in the top four to qualify for next season’s Champions League.
“There’s a long way to go, but we’re up there, even though we saw what happened last season (Athletic finished eighth), so we have to move forward with serenity,” coach Ernesto Valverde said.
Athletic took the lead in the minute when Yuri Berchiche ran down the left and fired the ball in front of goal for Berenguer to fortunately convert.
Berenguer scored his second goal before the break when the ball deflected into his inside the box and into the back corner for his fourth league goal of the season.
“I don’t play much this season, I have to take advantage of the opportunities I have, like today,” Berenguer said.
Real Sociedad slightly troubled Athletic goalkeeper Unai Simon in the first half and the home side held them back after the break.
In the end, Oyarzabal improvised a dead-chested shot to get Real back into the game and make Athletic sweat during the six-minute break.
Valverde’s side are made up of seven-point leaders Real Madrid and second-placed Girona, who travel to Almeria on Sunday without a win in a bid to become sole leaders.
Real Sociedad, sixth, are now nine points away from the top four.
“We didn’t get stuck into the battles with the right aggression,” Real Sociedad midfielder Mikel Merino told DAZN.
“It was a difficult defeat here today, we knew the issues were important, but not decisive, there is a long way to go in La Liga. “
Former Real Madrid playmaker Isco returned home with 14 minutes remaining to give Real Betis a 1-0 win over lowly Granada and move up to seventh, ahead of Las Palmas, who had beaten Villarreal 3-0 earlier.
Kirian Rodriguez struck twice as Las Palmas continued their impressive campaign with a convincing win over struggling Villarreal.
Francisco García Pimienta’s newly-promoted side provisionally moved up to eighth thanks to a comfortable win in Gran Canaria, which gave them the confidence of being able to compete in European football.
Villarreal, dumped out of the Copa del Rey on Monday by third-tier Salamanca, languish in 14th, four points above the relegation zone.
Kirian struck early and Juanma Herzog doubled the Islanders’ lead early in the day when he headed in a corner.
Las Palmas claimed victory when Kirian scored his second goal after the hour mark, helping his team in their Spanish Cup round of 16 clash against local rivals Tenerife and ending a four-game winless streak.
Villarreal have only won once in their last six league games and have not found form under coach Marcelino, appointed in November.
Real Mallorca came from behind to draw 1-1 with Celta Vigo.