Early in today's match between Arsenal and Chelsea at Stamford Bridge, Arsenal midfielder Alexis Sánchez turned to run down a hopeful ball over the top, nearly got on the end of it, and ended his run by plowing his hip through Chelsea goalkeeper Thibaut Courtois's head. Courtois appeared to be knocked out cold. He laid motionless for several moments, but stayed in the game after being looked at by team trainers.
Courtois would come off, finally, after he went to the ground again in the 23rd minute without any obvious contact. The trainers seemed to be attending to a cut on his ear once they got to Courtois, but they were concerned enough to force a substitution of Petr Cech, himself known for having suffered a nearly fatal head injury .
Top tier soccer leagues, including the Premier League, have introduced new concussion protocols. They are flawed even by the low standards of such rules in professional sports, and appear to have been ignored in whole here. The very first rule is that a player appearing to have suffered a head injury must come off the pitch to be examined by the club doctor. This did not happen today. A third-party "tunnel" doctor is to be supplied by the home side, and act as an independent spotter for potential head injuries (this is cribbed from the NFL's version of an independent spotter), but was also nowhere to be found.
Yes, a goalkeeper being involved complicates matters, because you can't play without a keeper, unlike an outfield player going off for a few minutes to be tested. Other organizations' protocols, like the newly introduced UEFA rules, allow for a three minute stoppage of play to evaluate a player, which is a better solution, though three minutes is not really enough time to properly evaluate a player, either. But the complications will need to be solved, because goalkeepers are frequently the ones on the receiving end of these kinds of hits.
Courtois was taken to a London hospital after he was taken off the field.