Red Bull have had a difficult start to the season and Verstappen, who missed out on last year’s title to McLaren’s Lando Norris by two points, is ninth in the championship after three races with a best result of sixth.
Red Bull are introducing a major upgrade to their car for Miami, when the season restarts after a break enforced by the cancellation of the Bahrain and Saudi Arabian Grands Prix.
This was tested by Verstappen at Silverstone last Wednesday and Mekies said it would address “a fair chunk” of their shortcomings
“One thing is sure, we haven’t solved everything,” Mekies said. “But there is no doubt that progress has been made into giving something more consistent to our drivers.
“How does that make you fit in the classifications? It’s impossible to know. But in terms of us alone on the track, in terms of giving a more consistent product to our drivers, I’m confident we have made some progress. Do we know if we cracked everything? No, we know we didn’t crack everything yet.”
Stella – whose world champions have had a more successful start to the season, including a second-place finish for Oscar Piastri at the last race in Japan – said: “There was always the idea to deliver sort of a completely new car, especially from an aerodynamic upgrades point of view for the North American races.
“I would like to stress that this is what I would expect of most of our competitors so not necessarily is going to be a shift in the pecking order.
“It will be effectively just a check who has been able to add more performance within the same timeframe, and we also have some performance to recover if we look at Mercedes and to some extent Ferrari as well.”
Mekies said he believed about 0.3secs of the Red Bull’s one-second-a-lap deficit to front-runners Mercedes was accounted for by the new in-house Red Bull engine.
“Unfortunately, the first few races confirmed that we have a lot of work to do,” he said. “It’s 360. But certainly on the PU side as well, we can see that competition has a clear advantage. So we see them clearly ahead of us.
“It doesn’t remove anything to the amazing job that the guys have done. But it’s just confirmed that we have been evaluating ever since we put the car on the ground in Barcelona and in Bahrain. So fantastic starting point, unbelievable starting point. But it’s a competitive business.
“We are quite a few 10ths of a (second per) lap behind them in terms of performance. Even more so in terms of chassis performance, to be clear. And so we know we have a lot of work to do ahead of us.”