Lando Norris won the Miami Grand Prix ahead of Max Verstappen following a well-timed Safety Car.
It fell such that it allowed Norris a cheap pit stop, and enjoyed a tyre advantage in the run to the chequered flag over second-placed Verstappen.
That followed a promising opening stint from Oscar Piastri, which saw the Australian maintain pressure on the race-leading Red Bull Racing.
McLaren had a substantial upgrade in Miami, totalling 10 different components across both ends of the car.
Norris had the complete upgrade while Piastri had only half – the difference worth a reported two-tenths to his team-mate.
“We know in the numbers how much we improved, and it’s material – you should see it in lap time,” Stella said of the Miami upgrade.
“Before we say the pace we saw [in Miami] is a representation of the future… I’m not going to put my signature on this statement.
“We take this positive, we take this encouragement. If anything, it’s even more energy to develop, possibly even faster than what we were doing.
“But in my view, if you want to fight consistently [with] Red Bull, we need to deliver another package like the one that we have delivered.”
A year ago, both Norris and Piastri were bundled out of Qualifying 1 in Miami, highlighting the strong turnaround in the team’s fortunes.
Back then, Stella made no secret of the fact the MCL60 missed development targets pre-season and the squad began the year behind the eight ball.
He spoke of an aggressive upgrade plan, which was delivered on at the Austrian and Singapore Grands Prix.
“I would like to be here saying ‘oh yeah, of course, it was all under control,’ he explained.
“We had a plan. It’s true, we had a plan. I could see in the ground that the development, especially in the aero department, was very promising – the department was starting to be on fire.
“We saw that we were increasing aerodynamic efficiency in the wind tunnel and the simulation but, first of all, we need to see, once you put it on track, will the data correlate?
“We know that we were very far in terms of how much downforce and efficiency we needed to add to the car,” he added.
“There was a plan. There were some very encouraging elements. But ultimately there was a lot of belief.”
The development within the team seen then has continued with the aim of the Miami upgrade to maintain the momentum and trajectory set out last year.
And while that has been the case, it’s not a silver bullet with the Miami performance benefitting from the race circumstances and the upgrades.
This weekend’s Emilia Romagna Grand Prix is another event expected to suit the McLaren, given it has historically performed well in Imola.
However, Stella is aware that inconsistencies almost certainly remain.
“In Japan, we were six-tenths away in qualifying from Red Bull,” he reasoned.
“In China, again, we were like a few tenths away.
“So it would be completely unrealistic to think that what we’ve seen [in Miami] is the updated picture of competitiveness.”