La Real arrived at San Mames having lost just one of their previous nine away games across all competitions (W5, D3), and they appeared well-equipped to handle the hostile derby atmosphere.
They were denied a fifth-minute opener only by some incredible defending, as Unai Simon saved from Goncalo Guedes one-on-one before Jesus Areso slid in to stop Unai Gomez converting the rebound.
The Athletic fans increased the volume in response to that double block, but their side failed to create anything meaningful in the final third.
The visitors only continued to look more dangerous as the first half wore on, and Simon made himself big to keep out a Goncalo Guedes header eight minutes from the interval.
But the Sociedad winger would not be denied for long, as the resulting corner from Sergio Gomez was played to the Portugal international 25 yards out, and he whipped a ferocious shot into the top corner at the near post to score his sixth goal of the season.
Sociedad goalkeeper Alex Remiro hadn’t been forced into a single first-half save, but he was left relieved when Aitor Paredes thumped a long-range drive just wide three minutes into the second half.
Normal service soon resumed, though, and Sociedad’s top goalscorer Mikel Oyarzabal missed a golden chance to move onto nine goals for the campaign when he dragged his shot off target with the goal at his mercy.
Oyarzabal must have feared he would be punished for that miss as Athletic pushed forward, but La Real’s defence stood firm, while the home supporters grew increasingly frustrated as a string of marginal refereeing decisions went against them.
The hosts were handed a lifeline seven minutes from time, though, when Brais Mendez lashed out at Paredes off the ball and received a straight red card - the third game in a row that Sociedad have had a man sent off.
That incident only further raised the temperature, and the roof came off when Ruiz de Galarreta equalised three minutes from time.
The substitute cut in from the left wing, beat two defenders as he burst into the penalty area and fired into the far corner to rescue a point for Athletic.
With this late twist, the hosts have climbed three places to 11th, though their winless run in LaLiga now extends to six games (D2, L4). Meanwhile, Sociedad will stay eighth for the time being and remain unbeaten under head coach Pellegrino Matarazzo (W3, D3).
Flashscore Man of the Match: Goncalo Guedes (Real Sociedad)
