Newcastle United have had to rule Allesandar Mitrovic and Dwight Gayle out of Brighton and Hove Albion's visit to St James's Park.
Mitrovic and Gayle both suffered concussions during Wednesday night's 2-0 EFL Cup win over Cheltenham Town.
FA guidelines stipulate that any player who suffers concussion must wait for six days before returning to the field.
And they will not be involved in Saturday evening's televised home game against Brighton.
Paul Catterson, Newcastle's head of sports medicine and science, said: "The treatment and management of concussion in sport has received deserved attention in recent years.
"We have to adhere to the guidelines set out by the FA in line with other competitive sports, which rightly puts the safety and health of players first."