Ewan (Lotto Soudal) won the bunch dash into Sisteron on Tuesday morning (AEST), taking stage honours after a drag race between the sprinters.
The Australian emerged late from the chaos of the sprint, flying down the barriers and passing Sam Bennett (Deceuninck-QuickStep) in the final metres to claim the victory.
McEwen, a triple winner of the Tour de France's green jersey, analysed his countryman's sensational win via the SBS touchscreen.
"Ewan was in 17th position with 300 metres to go," McEwen said.
"It was a really tight squeeze but what I loved about Caleb Ewan's sprint was that he fully committed to that gap.
"He thought to himself 'if it's going to close, I'm going to hit it as hard as I can, it's the only possible way I'll go through and the only way I'm going to get the victory on this stage'.
"It was absolutely brilliant."
WATCH Robbie McEwen's full analysis here or video at the top of the article.