In the General classification, the three leaders remained the same: the Belgian rider of BMC Racing's Greg van Avermat is the first, the second Briton Geraint Thomas of Sky, the third American Tja van Garderen of BMC Racing.
Degenkolb was forced to lead out the sprint but the German had enough power to hold off Van Avemaet and Lampaert and claim his first Tour stage victory.
"I was lucky I was on Fernando's wheel, because that helped me reaching the finish line in third position".
"Everybody said I'm done and that after this accident I will never come back and I said "No, I'm not done".
John Degenkolb (Trek) won Paris Roubaix back in 2015 but has had to come back from the wilderness and overcome some personal setbacks and serious injury to finally snare another major victory. When we got closer to the finish I was a bit nervous because of the head wind and I didn't think it was going to happen.
It was the second career victory at the Tour for Groenewegen. - Peter the Great - There are two teams who have an obvious chance of winning the Arras-Roubaix stage who do not have a leader to protect, and they are Bora-Hansgrohe with Peter Sagan and Quick-Step with Niki Terpstra, Bob Jungels and Philippe Gilbert, none of whom would be a surprise victor.
Among the favorites in the overall standings apart from Froome: Alejandro Valverde is fifth (1:31 behind); Rafal Majka sixth (1:32); Jakob Fuglsang seventh (1:33); Adam Yates ninth (1:42); Landa 10th (1:42); Vincenzo Nibali 12th (1:48); Tom Dumoulin 15th (2:03); and Bardet 17th (2:32).
"It's a miracle I made it back, it's a miracle I'm still in the Tour de France", a dust covered Bardet said at the finishing line.
BMC Racing Team confirmed Porte's abandonment from the remainder of the tour, saying it was "devastated".
It was a fraught day for all the favourites, but most will know it could have been worse.
That cobblestone challenge will be followed by a rest day on Monday before the race shifts to its first mountain stages in the Alps. Thomas lies second on the general classification, 43 seconds behind Van Avermaet.
The team protected Martin well throughout the 181km route, allowing him to match all the attacks and accelerations in the final kilometres of the race.