Tottenham boss Antonio Conte is facing an injury crisis in his forward line after Son Heung-min departed Tuesday's crucial win over Marseille before the half-hour mark.
Dejan Kulusevski and Richarlison are already sidelined with muscle and calf injuries respectively. And the bad news has now been added to after Son appeared to suffer a head injury at the Orange Velodrome.
The South Korean forward had challenged Chancel Mbemba for a high ball on the halfway line 29 minutes into the Champions League clash. But he headed the shoulder of the Marseille star and was helped off the pitch after receiving treatment.
It is possible Son will now have to go through the FA's concussion protocols in order to return to action. Spurs are able to utilise the Enhanced Care Setting pathway to check that Son is safe to return to play.
While that pathway is quicker than at non-professional clubs if he is symptom-free, it will still be six days before he is able to return. That means that he will miss the visit of Liverpool in the Premier League on Sunday.
The first stage of the pathway is an initial rest period of a minimum of 24 hours, during which Son must be symptom-free before progressing. The second step is light exercise, which will again take 24 hours if he is symptom-free.
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Son would then return to football-specific exercise before returning to non-contact training in stage four. If he is able to get through 24 hours of those stages symptom-free, a doctor will then assess him.
If that assessment is passed without Son presenting any symptoms of concussion, he can then return to full-contact training. Again that must last a minimum of 24 hours before the final stage of returning to contention for games.
As part of the protocols, it is stated that the whole return to play process must be supervised by a suitably qualified doctor within a structured concussion management programme. Clubs are also warned that they are minimum return to play times and in players who do not recover fully within these timeframes, return to play times will need to be longer.
Spurs assistant boss Cristian Stellini, who was in charge for the win in France in the absence of Conte, is remaining cautious about the attacker's status. He revealed Son was able to take part in the celebrations after Pierre-Emile Højbjerg sent Spurs into the last 16.
"In this moment, we don't know. We have to wait for a medical assessment, and we have to wait until tomorrow. Sonny feels better now. I saw him in the dressing room. He celebrated with us," Stellini said.
"We're not sure if it is concussion yet. It was an injury to his face, his eye is swollen. So we will wait for tomorrow."
Yves Bissouma was the man to replace Son, meaning Spurs changed formation from a 3-4-3 to a 3-5-2 system. If Son is absent on Sunday, then Conte could start with five in midfield, with Harry Kane and Lucas Moura his only fit senior forwards.
