The pair were in a select group of GC riders that crested the top of the final climb of the Mont du Chat before their races were irreversibly altered. The highly technical descent – as used in the Critérium du Dauphiné – was wet from rain, and when Porte locked up his back wheel in one of the corners he was forced onto the grass.
The move took the Australian down and back across the road, where he and his bike made contact with Martin. Both riders slammed into the right-hand side of the banking in one of the worst falls this Tour has seen. Martin was able to remount and although he crashed once more he finished the stage in ninth place, 1:15 down on stage winner Rigoberto Urán (Cannondale-Drapac). Porte was not so lucky and left the race in a neck brace, his ambition of winning the Tour over for another year.
"It's so slippery and I guess the organisers got what they wanted. I don't think anyone wanted to take risks there, but it was so slippery under the trees. Richie locked up his back wheel, went straight into the grass, just wiped out, and his bike just collected me. I had nowhere to go," Martin said after crossing the line in Chambery.
"We take the risks, but for sure today the route didn't help with the rain," he added.
"There was a lot of gravel on the road and a lot of fast technical downhills. If you're not safe in the first five riders…"
When Martin picked himself up off the deck his first concern was to check himself over, gather his bike and start again. His rivals were not waiting for him as they hurtled down the climb. Martin was only able to give Porte a quick glance before refocusing on his own race.
"He didn't look very well to me. He wasn't moving very much, but I was just trying to get going away."
The crash with Porte wasn't Martin's only incident in a significant day at the Tour de France. The Irishman almost came down in the fall that ended Geraint Thomas' race.
"I was very lucky the first time," he said. "Geraint went down and his bike hit my handlebars. I got through but my luck run out."
Martin in fact hit the deck for a second time on the descent of the Mont du Chat. After having received neutral service, he found himself without any adequate braking. The second spill wasn't caught on camera but it paled in significance to the first crash.
"I got a spare wheel off Mavic but I didn't have any brakes. I couldn't stop and went straight on. The second one wasn't really much. I just got a spare bike off the team car and got going again. I think it's just superficial wounds.
"I couldn't really follow the accelerations on the climb but after I crashed the second time, I was flying on the downhill and caught the group in front. We caught Nairo Quintana (Movistar) at the bottom and rode as hard as we could. It was a team time trial. It was a case of getting to the finish."
Martin's time losses to several rivals mean he has dropped from fourth at 25 seconds to sixth at 1:44 behind race leader Chris Froome (Team Sky), but in the context of a crazy day at the Tour it could have been much worse. Other rivals, such as Alberto Contador (Trek-Segafredo), lost far more time, and Martin, unlike Porte, is at least still in the race.