Rodrigo Bentancur suffered a nasty concussion in Tottenham's 1-1 draw with Leicester and rules will see him miss the Everton game this weekend.
Midway in the second half, from a Tottenham corner, the Uruguayan clashed heads with Foxes winger Abdul Fatawu.
Fatawu was fine, but Bentancur sickeningly hit the floor and was out cold for several minutes.
He was immediately treated by medical staff and was awake when he was taken off the pitch on a stretcher.
The former Juventus man was not taken to hospital and was assessed by the Spurs medical staff in the dressing room.
And ahead of the Everton match this weekend, we have a look at why he won't be playing.
Is Rodrigo Bentancur fit to play against Everton?
Based on the Premier League's concussion guidelines, Bentancur won't be allowed to play in this weekend's game against Everton.
This is because any player who suffers concussion in a match cannot return to competitive action for at least six days.
Tottenham's game against Leicester was on Monday, and they next play on Saturday, meaning the Uruguayan will miss Spurs' first home match of the season.
He will undergo a formal post-match assessment, and if that reveals no sign of concussion, Bentancur can return to first-team training.
Tottenham also used a concussion substitute, known as an additional permanent concussion substitute [APCS], and there are rules attached to using one of these.
Spurs must now submit medical information and a report on Bentancur's condition within seven days after using an APCS against Leicester.
The Premier League's relevant sub-section will check over this information and make sure it is all correct.
If everything is fine and Bentancur shows no delayed signs of concussion, the midfielder will be able to return to action against Newcastle United on Sunday, September 1.
Although Spurs fans will be disappointed he can't play against Everton, they will be pleased to know he's fine and the proper procedure was followed.
Speaking after the game about Bentancur, Spurs boss Ange Postecoglou said: "He is up and communicating.
"It is a head injury, and we will leave it in the hands of the medical team, but he is conscious and communicating.
"Nowadays we are always cautious in the moment."