Richie Porte crashed out of the Tour de France before John Degenkolb won a chaotic stage nine over the cobbles to Roubaix.
BMC's Porte, among the favourites for overall victory, crashed long before the first cobbled sector, just seven kilometres from the start in Arras.
The 33-year-old Australian appeared to be holding his collarbone before being taken away for x-rays.
He was not alone in suffering as Chris Froome, Mikel Landa and Rigoberto Uran also hit the deck in an action-packed stage, while Romain Bardet suffered a string of mechanical issues as the general classification was given a proper shake by the cobbles.
Greg Van Avermaet stayed in yellow, extending his lead over Team Sky's Geraint Thomas to 42 seconds by finishing second, but there were losses for Landa, Bardet, Uran and others while Froome and Mitchelton-Scott's Adam Yates moved into the top 10, both now one minute 42 seconds down.
Since the 2018 Tour route was announced in October, this day had been circled as the wildcard which could deliver a jolt to the race, and it did not disappoint.
The cobbles made up only 21.7km of the day's route, but brought with them a constant fight for position and battle of nerves, such is the likelihood of crashes and mechanical problems.
Porte did not make it far enough to see them, caught in a huge tumble early on as he crashed out on stage nine of the Tour for a second straight year, continuing a run of rotten luck when targeting victory in Grand Tours.
Froome recovered from his own tumble on the eighth cobbled sector to finish in a much-reduced peloton alongside Sky team-mate Thomas, but others were not so lucky.
AG2R La Mondiale's Bardet suffered a remarkable five separate mechanical problems, the last of them as he exited the final cobbled sector only six kilometres from home, but was able to limit his losses against the rest of the contenders to just seven seconds.
The French favourite largely did so by latching on to a group in which Movistar were driving the pace to help Landa recover from a spill 40km from home. The Spaniard survived the cobbles but managed to hit the deck on a stretch of straight tarmac as he took a drink.
The losses for Education First-Drapac's Uran were more considerable as he gave up almost 90 seconds to Froome and others.
It was a first career Tour stage win for Trek-Segafredo's Degenkolb, with the German able to hold off Porte's team-mate Van Avermaet and Quick-Step Floors' Yves Lampaert in a sprint to the line.
The trio had broken clear with a little under 20km to go and were left to contest the stage between themselves.
Although Van Avermaet retains yellow for now, it was in truth a dismal day for BMC. While Porte headed for hospital, their likely Plan B Tejay Van Garderen - who started the day just nine seconds off yellow - got himself caught up in crashes and conceded more than five minutes to effectively rule himself out of contention.
The riders now face a long transfer to Annecy, but have Monday's rest day before the race moves into the Alps and the true battle for yellow emerges, albeit without one of its biggest likely protagonists in Porte.