Lando Norris qualified second for last week's Dutch Grand Prix behind Max Verstappen, the latest evidence of the giant leap McLaren has made with its B-spec upgrade it deployed before the summer break.
That overhaul allowed it to challenge Mercedes, Ferrari and Aston Martin in the ever-fluctuating fight behind Red Bull, with no team being able to consistently claim the status of second-fastest team.
But team principal Stella cautioned the difficult mixed weather conditions across the Zandvoort weekend flattered McLaren. While it introduced a new rear wing to good effect, Stella thinks the team will need regular development to be second on merit.
"To be able to do that, we need to keep developing the car," Stella commented on McLaren's one-lap speed.
"Because I think, at this track, in normal, dry conditions potentially Mercedes could have been there with us. They were faster than us in Hungary. If you remember they had pole position, actually.
"So, I think the current package is not enough to be able to fight with Red Bull, certainly, but it's also not enough to be going to a race and say we're going to be the second fastest here.
"We need to introduce further improvements, which is what we plan to do for the next couple of races."
Source: Autosport