The Manchester City forward was expected to be sidelined for between two and four weeks after breaking a rib in the road accident last Thursday.
That would have ruled the 29-year-old out of Argentina’s final two World Cup qualifiers against Peru and Ecuador, but could have seen him in contention for City’s Premier League match at home to Stoke on October 14.
However, Villani believes Aguero will be out longer than first thought.
“He’s feeling very bad because he was really looking forward to coming to play and this incident, which had nothing to do with him, left him out of the two games,” Villani said.
“He’s going to be off the pitch for a month and a half.
“He can’t move in his house, nor get in and out of the car. He seemed very down to me because we wanted to be here.”
A six-week lay-off would rule Aguero out of both of City’s Champions League group games against Napoli, as well as four more Premier League games, including the home clash with Arsenal on November 5.
Sergio Aguero, who was in Amsterdam for a music concert performed by Colombian singer Maluma, suffered the injury when the taxi he was travelling back to the airport in crashed into a pole at 11pm.
He admitted afterwards his injuries could have been more severe, saying the “seatbelts prevented it from being worse”.
Aguero had been on a day off and City boss Pep Guardiola insisted he had nothing to apologise for.