For the Belgian star, this was his first individual win since the Tour de Yorkshire last year, as well as being his first in his new team colours, CCC. It was also the team's first in Europe in 2019 (and third of the season) and after last year's series of near-misses in the Classics, confirms that Van Avermaet is hitting top form just in time for his first big target of 2019, Omloop Het Nieuwsblad.
As if that was not enough, Van Avermaet's win came against a stellar line-up, where riders like Alejandro Valverde (Movistar), Luis León Sanchez (Astana ProTeam) and Matteo Trentin (Mitchelton-Scott) were visibly itching for a chance to raise their arms in the air - in Trentin's case, for what would have been the second time in 24 hours.
Instead, Van Avermaet claimed a victory that, as he pointed out afterwards, had a lot to do with his team-work as much as it did with his own individual ability. De Marchi played a key role by clamping down a late attack by Ben Hermans (Israel Cycling Academy) but the group effort had been another big factor in the equation as well.
"I'm very relieved and very proud to have got this win," Van Avermaet said afterwards. "At the end of the stage, there were four of us in front - [Lukas] Wisniowski, [Amaro] Antunes, De Marchi and me.
"We worked very well together, this race is a kind of test or preparation event, but the field is WorldTour level for me. That's why I appreciated this victory even more.
"It's always great to start the season with a win, particularly on a hard parcours, but I felt super all day.
"I was in a good position on the last switchback, second was perfect, and then I was hoping nobody came over me. So that's a good season start, the best one possible."
At the CCC team bus, half a kilometre away high on the main road out of Chera, there was much celebratory back-slapping and grinning at their first victory in Europe this season, with Jim Ochowicz's arrival on the race today seen as evidence that the veteran American manager had brought some good luck with him for the squad.
"With Greg, he's got that instinct for finishes like that, uphill, hard, that's what he does," Ochowicz told Cyclingnews. "But that's also what other guys like Valverde do well as well.
"For us coming out of Australia and in these first races in Europe, the team is showing its colours.
"We know we have more to do but this is a great start for us."
Ochowicz said he would like the squad to take 20 wins this first season, and the team now has three with the year's racing barely underway, but he said that he would not be raising his target despite the early success.
"We're not going to be making any adjustments," he said with a grin. "But for us, with Het Nieuwsblad coming up, that's Greg's season [targets] so we have to be good early and hold on as long as we can."