“The team did a stellar job today and worked the whole day really hard to support our GC leaders and help me in the finale if it all came back together," McCarthy said.
After 15km of racing, Thomas De Gendt (Lotto-Soudal) and Christopher Juul-Jensen (Mitchelton-Scott) led the race before another six-rider group, which included Australian Brendan Canty (EF Education First-Drapac), bridged across to help build an advantage of more than six minutes after 55km of racing.
The break sustained its effort until it was shut down with three kilometres remaining with a bunch sprint looming before McCarthy capitalised on the lead-out from BORA-hansgrohe.
"Felix [Grossschartner] and Cece [Cesare Benedetti ] rode super strong to control the race in the last 30km, then Gregor [Mühlberger] came in the last five kilometres to the front and did a great lead-out for me.
"I started the sprint early and gave it all. I am really happy with this victory and want to thank my teammates for their support.”
Alaphilippe, winner of the first two stages, remains eight seconds clear of Primoz Roglic (LottoNL-Jumbo) on the general classification with Stage 4 a flat 19.4km individual time trial around Lodosa next up for the peloton.