From the launch of the MCL60, Stella stressed a need for the team to remain “realistic” as it started the campaign with an underbaked design.
In the meantime, he led an overhaul of the technical division by getting rid of director James Key before hiring David Sanchez from Ferrari and experienced Red Bull chief engineer Rob Marshall.
A major upgrade for the Azerbaijan Grand Prix represented how the car should have started the year and since then, the team has battled to keep pace with rivals in the development war.
With the calendar moving away from street tracks that dominated the start of the campaign to the conventional Barcelona circuit last weekend, Stella reckoned the more representative Spanish GP layout had offered information on why the MCL60 switches behaviour overnight.
This came after Lando Norris qualified third before sustaining first-lap damage to finish 17th. Meanwhile, rookie team-mate Oscar Piastri started ninth on the grid before falling to 13th.
Stella said of a straightforward race that passed without a safety car or rain: “I think the only thing that it really adds is [the information on] this almost opposite behaviour of what happens in qualifying compared to what happens in the race.
“We don't only have to look at the aerodynamic behaviour of the car, and we know that we have to take a step forward from an aerodynamic point of view.
“But clearly, we also need to get our tyres to work in a better range during the race.
“This was quite clear already but this weekend, I think we took the two extremes of being competitive in qualifying, with no issues with warm-up when some of the people were talking about warm-up with our surprise.
"[In the race] a lack of pace, other people like Mercedes had very, very good degradation. So, that's the main takeaway.”
McLaren has struggled in hotter conditions so far this season, but the cool qualifying session after a rain-affect FP3 - plus the early eliminations of Charles Leclerc, Sergio Perez and George Russell - allowed the team to surpass one-lap expectations. However, track temperatures rose by 20 degrees for the race.
Stella continued: “As I tried to describe [qualifying], the conditions were very special, suiting our car exceptionally. Also, I think some of our competitors just underdelivered. So, I think it was just not really representative of the pecking order.
“With the hotter conditions, not [having] the benefit of the new tyres, we just ended up not having enough pace.
“But at the same time, also quite high tyre degradation, which could be simply the counterpart of the fact the car seems to be preparing new tyres so well.
“[That is] obviously something that we need to improve if we want to stay in the race in hotter conditions.”
