The Barcelona attacker was stretchered off in the closing minutes of the Selecao's 2-1 victory over Colombia in Fortaleza, and Scolari is downbeat about the 22-year-old's chances of being fit for Tuesday's game in Belo Horizonte.
Scolari told reporters: "He was kneed in the lower back. We don't have the exact information but I can guarantee it won't be easy for him to recover based on what the doctor told us and the pain he is in.
"It will be very difficult for him to play."
Neymar is Brazil's top scorer in the tournament so far, with four goals to his name.