Peter Sagan (BORA-hansgrohe) lost his chain during the sprint at a wind-swept Lavaur, while rival Julian Alaphilippe (Deceuninck-QuickStep) also suffered an untimely mechanical issue.
A messy sprint to the line ensued from the reduced peloton, with 30-year-old Sagan unable to recover - finishing in 13th as Wout van Aert (Jumbo-Visma) claimed the stage.
Although Sagan and Alaphilippe were disappointed not to have placed higher on Stage 7, the duo were relieved their mechanical mishaps didn't result in a crash.
"I was unlucky in the sprint because my chain got blocked. It was a mechanical problem, yes, but that wasn’t the whole story," Sagan said.
"I’m lucky to not have crashed. After that, it was impossible to get to the front.
"I'm disappointed because we controlled the race all day. Everything seemed like it was very good and in the end I had bad luck in the final - I had the chain drop off and I missed a lot of points. That's f****** cycling."
McEwen, a triple winner of the Tour de France's green jersey, analysed the final sprint and where things went awry for Sagan.
"It was a chaotic stage," McEwen said.
"Sagan went shoulder to shoulder with van Aert and came off second best.
"Alaphilippe then looked for an opening and Sagan had a moment of panic.
"As Christophe Laporte takes that wheel, it all starts to unravel for Peter Sagan."
