Romain Bardet recovered from three punctured tires.
Spanish rider Gorka Izaguirre had the unusual experience of his rear wheel buckling to the point that it looked like something out of a scrap heap.
To make matters worse for his team, its best option to take over from Porte as leader had a horrendous day on the cobbles.
BMC's Greg Van Avermaet doubled his advantage in yellow to six seconds by winning the bonus sprint.
Although Van Avermaet retains yellow for now, it was in truth a dismal day for BMC. It would have been nicer without all the crashes, but at the end of the day my bike was faultless, we made it to the finish line and we're still in the fight for the podium.
The Belgian - not renowned for his climbing abilities in the saddle - sits two minutes and 22 seconds ahead of Geraint Thomas in the general classification, while four-time champion Chris Froome is just under a minute further adrift in sixth place.
My back's against the wall, says Cavendish
"I had a little tumble halfway through, but I'm just grateful to get through the stage without having any major issue", he said, aware that most of his rivals finished on the same time but that Richie Porte crashed out after just 10km.
Porte was taken to hospital for x-rays on what is suspected to be a broken collarbone. "It was really painful", Baldato said. "I followed Sagan, but following him is pretty sketchy - he bashes everyone else out the way so you do get a clear run following him".
It was an impressive performance from Bardet to limit his losses, given the AG2R La Mondiale rider suffered three punctures during the stage.
Van Avermaet won the single-day cobblestone Paris-Roubaix race in 2017.
Degenkolb was the victim of a serious training accident in January 2016 when a vehicle drove into oncoming traffic. "When you hear a doctor say that you know it's no good", he said.
"That was incredibly hard and I have a new level of respect for the guys that ride Paris-Roubaix".
"I'm not 100 per cent sure we should be putting cobbled stages in the Tour de France", he said.