Paris Saint-Germain star Neymar suffered an early injury in Brazil's friendly against Cameroon on Tuesday in Milton Keynes.
The Brazil captain left the pitch for treatment as Allan squandered his side's first chance, before Neymar returned to the field and fired over the crossbar from 25 yards.
That effort only appeared to further aggravate an apparent groin injury, however, as Neymar immediately went down and gestured to the bench that he would have to be replaced.
Richarlison came on in the former Barcelona man's place after just eight minutes, with the injured star stopping briefly on the bench before heading down the tunnel.
PSG face Toulouse on Saturday, with a crucial Champions League meeting with Liverpool to follow next Wednesday.
Neymar's first season in France was disrupted by injury, a broken foot suffered in February impacting Brazil's preparation for the World Cup.