Concern over effects of blows to the brain is rising in contact sports and incidents in Premier League appear on the increase
Romelu Lukaku being knocked clean out scoring a goal for Everton at Upton Park that he admitted he could not remember; England's latest saviour, Andros Townsend, hurtling over the advertising hoardings at White Hart Lane and crashing into a photographer before playing on; Mathieu Flamini clashing heads with Norwich City's Alexander Tettey and being substituted with double vision.
Even before the avalanche of criticism that greeted the decision by André Villas-Boas, apparently with the consent of the club's doctor, to leave Tottenham's goalkeeper, Hugo Lloris, on the pitch at Goodison Park, the prevalence of head injuries among top-flight footballers appeared to have increased during the opening months of the season.
In the absence of conclusive figures from the Premier League and the Football Association, it is impossible to say whether there has been an increase in incidents, or if it is simply that those that have happened have had a higher profile. Part of the reason may be that the debate surrounding head injuries and concussion in other sports, most notably rugby and American football, has hit the headlines in recent weeks.
In rugby union, there has been a backlash against plans to trial a scheme to reduce the length of enforced absence from the field to as little as five minutes following a concussion assessment at the side of the pitch. Despite assurances that the protocol would be safe, some say the new International Rugby Board rule could put players in danger in an era when the sport is faster, and players are bulkier and stronger, than ever.
In the US, the National Football League has agreed to pay $765m to 4,500 former professionals who joined a class action lawsuit alleging that the NFL spent decades hiding the harmful effects of the sport on the brain. The NFL settlement admitted no liability and critics said it failed to deal with the ongoing issue.
Just as rugby was accused of burying its head in the sand when the scale of the problem in American football became clear, so football is likely to face some difficult questions. As a completely different sort of contact sport, the number of instances where a player is likely to suffer concussion or a serious head injury is going to be smaller but the potential consequences are just as serious.
In 2008, the third Consensus Conference on Concussion in Sport took place at Fifa's HQ in Zurich and established what was described at the time as a breakthrough agreement across football, rugby union, the International Olympic Committee, the International Ice Hockey Federation and the International Equestrian Federation that any player or rider suffering concussion should leave the field immediately. The decision was ratified last November at the fourth edition of the conference.
The autobiographies of footballers are littered with references to concussion, smelling salts, shaking off blows to the head or playing on while not being entirely sure where they were. Michael Owen describes taking an "almighty blow to the head" during the friendly against Morocco in which he scored his first international goal.
He says that following a later incident at Derby County he had "whiplash for a week" and swore he would never again use the word concussion unless he was "clinically unconscious".
Those international conferences, which began in 2001 and led to a common protocol for determining whether a player was suffering from concussion, and the growing collaboration between medical staff in a range of sports, indicate the extent to which the condition has moved up the agenda in recent years. The incident at Goodison, and the other high-profile examples witnessed this season, may highlight a gap between the rules and reality.
The Premier League's rule 0.9 states: "Any player, whether engaged in a league match, any other match or in training, who having sustained a head injury leaves the field of play, shall not be allowed to resume playing or training (as the case may be) until he has been examined by a medical practitioner and declared fit to do so."
The FA has a "policy", but not a hard-and-fast rule, that a player who has been substituted for a serious head injury or concussion should not return to playing or training for five days.
Both of those rules appear to vest huge responsibility on the club doctor on duty on the day. It is for them to determine whether the player in question has suffered concussion and, as such, should be removed from the field of play.
The Spurs head of medical services, Wayne Diesel, said: "Once the relevant tests and assessments were carried out we were totally satisfied that he [Lloris] was fit to continue playing."
But, as the Professional Footballers' Association argues, perhaps the time has come to take the decision out of the hands of the doctor on duty and require any player who is knocked unconscious or suffers a serious blow to the head to be removed automatically.
That would risk inviting a round of debate over who should have the final say over whether a player should leave the field, but – in an area where all the medical advice urges extreme caution – it might avoid club staff being placed in an invidious position.