"It was a very heavy slam, but seatbelts prevented it from being worse", he said.
"The first impression is he has broken the rib", City manager Pep Guardiola said. "It hurts me badly".
Premier League power Manchester City confirmed the incidenta Friday morning on its official website.
The news will also come as a big blow to Argentina, who host Peru in a crunch World Cup qualifier next month.
Asked on the timeline for his return, Guardiola said: "I don't know, I am not a doctor".
"I think days off are to be happy", Guardiola told reporters. "I would prefer to be with Mendy, with Kompany and with Sergio Aguero [but] we will play with eleven". If they decide to go there, they decide to go there. "It is OK for me".
He'll now have to wait to pass that tally and it has been reported City will be without his services for around two months following the crash in the De Boelelaan area of Amsterdam.
"There's a small bend in the street right there and presumably the chauffeur lost control of the wheel", said a spokesman. Two people were taken to the hospital.
Pictures on social media appeared to confirm the incident.
Aguero's former club Independiente have since sent a tweet wishing the forward well, saying: "Strength and quick recovery. All @Independiente is with you at this hard time".
Mendy has ruptured an anterior cruciate ligament and is facing a lengthy spell on the sidelines after undergoing surgery.
Guardiola said the French global would have surgery on Friday and be out until April.
"I don't like to train everyday because I think players need to rest mentally and physically, and they can enjoy their lives".
The 29-year-old is now chasing City's all-time scoring record, lying just one strike behind the mark set by Eric Brook, who netted 177 times for the club between 1927 and 1940.
The injury would rule Aguero out initially for Saturday's EPL clash with Chelsea and a crucial pair of World Cup qualifiers for Argentina against Peru (October 5) and Ecuador (October 10).
Argentina are fifth in the South American group standings for Russian Federation 2018 and need to move up a place to avoid facing a home and away playoff against New Zealand.