McNulty jumped into the early breakaway that formed on a climb in the opening kilometres of the 189 kilometre stage from Saint-Just-Saint-Rambert to Saint-Sauveur-de-Montagut.
Owain Doull (EF Education-EasyPost), Matteo Jorgenson (Movistar), Michael Mørkøv (QuickStep-AlphaVinyl), Ruben Fernandez (Cofidis), Harm Vanhoucke (Lotto Soudal), Anthony Turgis (TotalEnergies), Laurent Pichon (Arkea-Samsic), Valentin Madouas (Groupama-FDJ) and Franck Bonnamour (B&B Hotels-KTM) joined McNulty in the attack. They established a six-minute gap by the top of the climb, and with Matteo Jorgenson the main threat to the overall lead of Wout van Aert (Jumbo-Visma) at six minutes and 26 seconds in arrears at the beginning of the day, they largely maintained that lead throughout the stage.
The decisive moment came out the Col de la Mure, the imposing climb the last major climbing test on a day with four other categorised ascents. McNulty dropped back to his team car to drop off his arm warmers, then accelerated from the back of the group with six kilometres of the climb and 36 of the stage left to race.
The American quickly got a large lead, with Bonnamour, Jorgenson and Vanhoucke the most prominent in the chase from the breakaway. McNulty soloed away to a massive win by the finish, his first in the WorldTour, putting nearly two minutes into his former companions by the finish, with Bonnamour finishing second and Jorgenson third.
It was a remarkable turnaround for the 23-year-old, who had been thinking about abandoning the race after his poor start to the race.
"I was debating even continuing on or just resetting, so from considering not even starting today, it's incredible," said McNulty. "Today everything went according to plan, I got into the breakaway and had good sensations throughout the stage.
"Arriving at the penultimate climb, the team gave me the green light if I was feeling good and I decided to attack. This is a victory that definitely gives me morale to keep giving my best and aim to do even better.”
Back in the peloton, it was still a big battle on the Col de la Mure despite the stage win not being up for grabs. Nairo Quintana signalled his intentions to fight for the overall win by sending his Arkea-Samsic team to the front, with most of the Jumbo-Visma team dropped, including race leader Wout van Aert.
However, teammate Primož Roglič was second overall at the start of the day, and never looked in serious difficulty as Australian teammate Rohan Dennis took up the pace-making at the front of a much-reduced peloton.
Guillaume Martin (Cofidis) attacked clear, and held nearly a minute's advantage by the top of the Col de la Mure, with still 30 kilometres to the finish line. Daniel Martinez (INEOS Grenadiers) also attacked on the remaining uncategorised climb, with Roglič marking moves of Simon Yates (BikeExchange-Jayco) and Alexsandr Vlasov (BORA-hansgrohe) and even launching an attack of his own that saw Martinez and Martin recovered.
From there, it was a steady run to the line with most of the pre-race favourites maintaining their position on the standings.
Watch the full replay of the action from Stage 5 on SBS On Demand via the link below.
Paris-Nice continues with Stage 6, the longest of the 2022 edition of the race that will see the peloton tackle a similar medium mountain stage from Courthézon to Aubagne. Watch from 0015 AEDT on SBS and SBS On Demand, or catch up with the action the following day on SBS On Demand.
