Stella has been left in awe of his young driver's progress in 2023 as he rapidly acclimatised to the hectic world of Formula 1.
While there is still much for the 22-year-old to learn, the early signs have been overwhelmingly positive.
“One of the key enablers why you can go so rapidly is just the man behind the driver,” Stella said when asked by Speedcafe what impressed him most about Piastri.
“He's so calm. I think he's so good at keeping himself in a status in which he can use the best of his talent.
“I don't have that quality,” he admitted.
“I have to very actively think about what am I thinking? What are my emotions? I have to think about my psychology to actively keep myself in the most productive state.
“For Oscar, this seems to come quite naturally.”
Having worked with two drivers considered among the very best in F1 history, he is therefore in an educated position to pass judgement on Piastri.
“He has, potentially as a natural gift or maybe he worked towards in his young career, I don't know, but certainly he's remarkable,” Stella declared.
“And even when I've seen great drivers, currently or in the past, all of them sometimes underperform because they don't stay in the status in which they give their best.
“I think for Oscar, this is natural.”
Piastri ended the 2023 season ninth in the points standings, a fine result for a rookie who only received a competitive package mid-season.
During the year, he developed a trademark approach, building into a weekend during practice before delivering when it mattered in qualifying.
Learning how to manage the tyres proved a season-long lesson, with Pirelli's rubber notoriously sensitive to overheating.
That saw the Aussie spend the final day of running focused on getting a better understanding of how to get the most out of the tyres during the Abu Dhabi post-season test.
With the 2023 season now over, Piastri will briefly head back to the United Kingdom before taking a break over the Australian summer.
F1 returns with pre-season testing in Bahrain from mid-February.