Back from his post-Euro 2016 holidays, Bale was the only member of the renowned 'BBC' forward line who was fit enough to play in Sunday's game, as Zinedine Zidane's team travelled to San Sebastian in the midst of an injury crisis, with five regular starters unable to make the squad. 

As well as star forwards Cristiano Ronaldo and Karim Benzema, Luka Modric, Keylor Navas and Pepe were also ruled out, but it didn't stop Madrid earning a convincing win at a notoriously tricky venue, thanks to Bale's two goals.

"I'm happy for him," said Zidane. "Physically he's behind the others and you couldn't tell. He started in the best way, with an early goal. He's already said it's an important year for him, and he's showing that."

Bale was picked despite having appeared in just one friendly in pre-season, but the Welshman got Madrid off to a flying start, leaping into the air to powerfully nod home Dani Carvajal's tempting cross in only the second minute.

Alvaro Morata nearly scored his first goal since returning to Real Madrid but, after a clever dribble, his strike was deflected behind for a corner. 

A Toni Kroos effort met the same fate, with goalkeeper Geronimo Rulli quick to get down to tip the German's drilled strike behind.

Real Sociedad had a good opportunity to level on the half-hour mark, but former Madrid man Asier Illarramendi opted to pass to Juanmi instead of shooting when well placed and the ball didn't reach his team-mate. 

It was an end-to-end affair, with Morata denied again by Rulli, while youngster Asensio, picked ahead of James Rodriguez and Isco, continued to bewilder defenders with his quick feet on his first start in La Liga for the European champions.

The forward scored Madrid's second goal in the 40th minute with an effortless lob after he was sent through on Rulli's goal by Raphael Varane's pass, scooping the ball over the goalkeeper with ease.

Zidane acknowledged the 20-year-old's fine form was giving him selection problems.

"I had to decide and he went out from the start and did well. It's a headache picking the line-up. Asensio had a great game, but so did (Mateo) Kovacic and others. The important thing is the team," Zidane said.

Morata was seeing a lot of the ball in the second half but was foiled at every turn, being booked for diving in the area before his shot was saved and Kroos cracked the rebound against Rulli's crossbar. 

The goalkeeper was called into action to tip a Mateo Kovacic piledriver wide as Madrid continued to turn the screw, although despite their dominance they could not stretch their lead until Bale ran through, rounded Rulli and squeezed the ball home with the last kick of the game.
                  
Atletico held                  
                  
Home coach Eusebio Sacristan blamed himself for the heavy home defeat.

"The person most responsible for what happened is me and if we are capable of facing up to Real Madrid, that is my responsibility," he explained.

"The players are absolutely committed, but it's clear we have to work hard to improve and correct our errors as soon as possible."

Atletico Madrid had to settle for a 1-1 draw at home to Alaves after a crazy finish to their game at the Vicente Calderon.

Diego Simeone's side won a debatable penalty three minutes into stoppage time when Victor Laguardia was adjudged to have fouled Fernando Torres and summer signing Kevin Gameiro netted from the spot.

But there was still time for Manu Garcia to equalise for the newly promoted visitors with their first shot on target of the evening.

Earlier, Sporting Gijon beat Athletic Bilbao 2-1, while champions Barcelona opened their campaign in style on Saturday by beating Betis 6-2 with Luis Suarez scoring a hat-trick and Lionel Messi netting twice.

Also on Saturday, Sevilla beat Espanyol 6-4 in an incredible game.