The image of Fernando Torres lying prone in a worrying state on the Estadio Riazor turf was a frightening image to anyone who watched it.
Torres' concussion has now reopened the debate about the danger of blows to the head in football.
Studies have been underway to determine the risks and how best to minimise the dangers that emerge from concussions.
In the United States, children below the age of 13 have been banned from heading the ball, until they will have a fully formed brain.
The country has also brought greater clarity on the topic of brain injuries in the NFL, where the American Academy of Neurology ruled that at least 40 percent of retired players show signs of traumatic brain injury left over from their playing days.
That research came from tests that were conducted on 500 retired players who played in the NFL for a period of at least five years.
It also showed that half of ex-players have problems with executive function, 45 percent have problems with learning or memory, 42 percent with concentration and 24 percent with spacial function.
At the Universidad Camilo Jose Cela, studies are being carried out to determine the risk in European football at both the professional and amateur youth levels.
So far, they have determined that in football, head impact injures are caused by three main factors: collisions with other players as was the case with Torres, with parts of the stadium such as the goalpost or advertising board and finally and most worryingly, with the ball itself.
Figures from various studies show that players who head the ball more than 800 times a year have problems with memory loss.
The statistics are even more worrying in women's football as women suffer more concussions than men, with the results almost doubled on a sample of 10,000 games.
"After surveying physios, doctors and coaches, 94 percent of the athletes in the country don't take any tests before the start of the season," said Alvaro Garcia-Romero, a leading researcher in the field.
"This is a problem because, to analyse the evolution of injuries to the head, they should be compared to previous results and the tests take less than 10 minutes."
In recent times, it has become more commonplace to see players wearing protective headgear such as Cristian Chivu, following a collision with Sergio Pellissier, and Petr Cech, after he suffered a similar injury in a challenge with Stephen Hunt.
At the end of 2015, the goalkeeper asked to get rid of it as he felt it was causing him problems with hearing and communicating with his defence but doctors forbade it.
Carles Puyol, Martin Demichelis, Thiago Silva and John Terry are other prominent names who have been forced to wear protective gear on their heads after injuries to that area.
A more serious case was that of Patrick Grange, an American semi-professional footballer who sadly passed away in 2012 after suffering an injury to his skull.
According to Garcia-Romero, the way to act with these kind of injuries is clear.
"The first thing with head problems is to rule out any injury to the neck and then with the help of another person, an airway is opened or the person is placed in a lateral safety position," continued Garcia-Romero.
"If you play again too soon after it, either in that game or the next one and suffer another blow, it can lead to a macroscopic injury or even death."
That is the tragic situation which, Garcia-Romero said, could have came about in the recent fixture between Osasuna and Las Palmas.
"Berenguer played on for seven minutes after suffering a heavy blow to his head in a collision with David Simon," he stated. "If he had been hit hard during that time he could have suffered a very serious injury.
"If it was a blow to his head, the injury could have been permanent or even lethal."
In those kind of cases, he was insistent that it was then up to the officials to step forward and take action by refusing to allow the player to continue.
"The players must be aware that what happened to Torres could happen to them," he concluded.