Barcelona sporting director Deco has said the club want an explanation of the process which led to Robert Lewandowski's goal being disallowed in Sunday's defeat at Real Sociedad.

Lewandowski's 14th-minute strike at Anoeta was ruled out after the semi-automatic VAR offside technology (SAOT) ruled his toe was fractionally offside, with La Real going on to win 1-0.

Barça coach Hansi Flick said the decision was "wrong" and a "huge mistake," with some images appearing to show defender Nayef Aguerd's foot ahead of Lewandowski's at the moment Frenkie de Jong played the pass.

"I don't think VAR, and not just because of this game, has fixed what in theory it was going to fix," Deco said in an interview with Mundo Deportivo on Wednesday.

"Some things have improved, but in other areas we still have one person's interpretation. We still have controversial decisions, like the one at Anoeta on Sunday, which was probably incorrect.

"I don't understand if it's semi-automatic, not automatic, if someone has to press the button ... It's like having a car and not knowing if it's automatic, if it's hybrid ... someone will have to explain it to us.

"Why is it semi-automatic? I am lost. I still don't know if the boots were yellow [Lewandowski's] or black [Aguerd's] ... We don't want to go there because we don't want excuses, but there's a question: what happened?

"Where's the error occurred, if there's an error? If not, no problem, but we need an explanation because we're lost with what semi-automatic means, if there's an involvement from VAR, if the referee really can't do anything.

"If the semi-automatic system doesn't work, then we need to return to another system. This isn't a Barça issue, it's about improvements for all teams. Tomorrow it could be a bad decision for Atlético Madrid, Real Madrid, Sevilla, Rayo Vallecano, whoever."

SAOT was introduced to LaLiga at the start of the season. It is increasingly used in the biggest competitions in the game, but not universally. The Premier League, for example, has delayed its roll out while it waits for more testing to be completed.

It is effectively a support tool for the VAR and on-field officials to help make faster, more reproducible and more accurate offside decisions.

The technology uses 12 dedicated tracking cameras mounted underneath the roof of the stadium to track the ball and up to 29 data points of each individual player, 50 times per second, calculating their exact position on the pitch. The 29 collected data points include all limbs and extremities that are relevant for making offside calls.

Barça believe the system failed when it suggested Lewandowski was offside, but the Refereeing Committee in Spain (CTA) stand by the decision and insist it was correct.

Barça's defeat to Real Sociedad also came without Lamine Yamal. It was the second league game the 17-year-old has not started this season and the second that Barça have lost.

It illustrates the growing importance of Yamal to Flick's side, with Deco saying comparisons with Lionel Messi are to be expected even if there are differences.

"The comparisons [with Messi] aren't a problem for Lamine, it's an honour," he added. "I don't know if it's a good or a bad thing, it depends on Lamine, but he's growing, developing and I don't see any problem.

"Comparisons are going to happen. Football is emotion, passion, it's normal that people speak, compare, remember.

"Lamine is unique, he has his own story. It just so happens he's at the same club as Leo, with both breaking through young, although in different situations. Leo entered a more established side, whereas Lamine is being part of the revolution, the reconstruction of the club. But it's nice, if the comparison is there then it means he has something good about him."