Lazio playmaker Hernanes is expected to be out for at least a month after he was knocked unconscious on Tuesday evening.
The Brazilian midfielder clashed heads with Juventus' Luca Marrone, and admitted afterwards that he had 'no idea what happened'.
But the capital club have confirmed today that the 27-year-old will have an MRI scan next Monday, before undergoing more tests a few days later.
And Rome-based newspaper Corriere Dello Sport have claimed that the influential attacker will miss at least four weeks on medical advice.
It means the former Sao Paulo man will be out of action for matches against Napoli, Milan and Borussia Monchengladbach.