Robert Lewandowski scored a brace as FC Barcelona cruised to a 4-1 victory at Real Sociedad on Sunday, their first win of the new LaLiga season.

Spanish teenage sensation Ansu Fati came off the bench in the second half and took charge of the proceedings with two assists and a goal.

Fati had been struggling to recover after a series of knee surgeries in the last two years.

Lewandowski, who was celebrating his birthday, opened the scoring in the first minute of the game, rifling in a shot after a great pass from Alejandro Balde inside the penalty area.

But Alexander Isak equalised five minutes later after latching onto a pass from David Silva.

FC Barcelona struggled to break the deadlock until coach Xavi Hernandez sent on Raphinha and Fati in the 64th minute, with both proving crucial to the visitors’ success.

First, Fati assisted Ousmane Dembele with a brilliant heel pass after a fine piece of individual play from Raphinha.

Then Fati finished a beautiful team effort to assist Lewandowski for their third goal.

The Polish striker returned the favour 10 minutes later, enabling 19-year-old Fati to score FC Barcelona’s fourth to wrap up the points.

“It was a difficult game. It always is when you come here,” Xavi said after the match.

“We played with more patience. Like in the second half, we’re much better. We lacked that in the first half.

“We spoke at the break about attacking the space better. That is what we needed to do.

“We deserved to win. It’s a good result for us. We played well in spells.”

The FC Barcelona coach also addressed the tactical changes he made that had such a big effect on the outcome of the game.

“It depends on the game, how the opposition play, the level of risk required, on many things,” Xavi said.

“Today we made attacking changes, bringing on Raphinha and Ansu for Balde and Ferran [Torres].

“We were basically playing with five or six forwards. It is all about risks and how many you need to take.”