The final sprint saw a tight group come together as carnage ensued around the final bend with Ewan sliding into Sagan, allowing Tim Merlier (Alpecin-Fenix) to cross the line first followed by teammate Jasper Philipsen, with Nacer Bouhanni (Arkea-Samsic) in third.
And despite Ewan crossing the line, he was taken to hospital for treatment and Lotto Soudal later announced the unfortunate news that the 26-year-old had abandoned the race due to a fractured collarbone.
Speaking before the announcement that Ewan was out of this year's Tour, McEwen - a triple winner of the Tour de France's green jersey - analysed the incident, while taking aim at the race organisers.
"The stage finale shouldn't have occurred and a lot of others agree," McEwen said.
"Riders in the Tour de France - after finding out about the route - they asked the UCI to take the times for the general classification at eight kilometres to go, to try and avoid the situation we ended up with.
"But it fell on deaf ears - there's been absolute carnage, a lot of injuries, a lot of Tour hopes dashed and in the early part of the Tour, you just shouldn't be sending a raging peloton down narrow winding roads like that.
"It's too late now, the damage is done.
"Caleb Ewan was looking to go for the inside of the corner but Tim Merlier was also looking for the shortest route and Peter Sagan didn't want to lose his position in the wheel of Merlier.
"As Ewan comes through the inside, it's disaster.
"Ewan slid himself up the inside and, in fact, he overlaps the wheel of Merlier.
"As Merlier gets out of the saddle, his bike moves backwards just a touch towards Caleb.
"He's a little bit too close, there's a touch of wheels and Caleb was angled to the outside. It capitulated Caleb over the bars and took Sagan out with him."
The Tour de France continues tonight with Stage 4 from Redon to Fougeres and you can catch all the action LIVE on SBS and SBS On Demand from 9:30pm (AEST), with SKODA Tour Tracker App starting from 9:15pm (AEST).
