Those performances won the Australian countless plaudits over the course of the year, with many impressed by his cool, relaxed manner under extreme pressure.
But according to Stella, 2023 was simply a taste of what is to come as the 22-year-old grows and develops in the sport.
In today's episode of the KTM Summer Grill for Speedcafe, Stella offered a glowing endorsement of his young driver.
“But I'm thinking he is at the start not because he's a rookie; he's at the start because the sense of potential you perceive working with Oscar is like, wow!
“I don't know how far he can go. I can only see the start. I have almost no sense of how far he can go in this journey.”
Piastri entered F1 after a year on the sidelines and following a high-profile arm wrestle over his services.
It underscored the esteem in which he was held off the back of a stellar junior career that netted three championships in successive years.
Aware of the potential the Melburnian has, Stella is conscious of working to nurture and develop it to make Piastri a more complete driver.
“It's important we focus on this concept of, it's the start, we are creating the foundation,” Stella explained.
“We know the strengths, we need to work hard to identify the opportunities, accelerate on developing the opportunities, the limitations, if you want, the weaknesses, and consolidate the strengths.
“For me, what is important is just a sense of journey,” Stella added.
“I've said already in the past the results take care of themselves, so what you really have to focus on is every day, try to be better than yesterday. And tomorrow, be better than today.
“That's the ethos that we try to have at McLaren. Certainly, I can see in Oscar, and certainly, that will be the main advice I will keep giving Oscar.”