Tost caused a stir when he criticized his engineers during the FIA press conference at the Saudi Arabian Grand Prix.
Other team bosses were surprised the Austrian would punish his staff in public, even given his reputation for being outspoken.
Asked that time about the team’s early-season performances, he made it clear that he had been led throughout the winter to believe that the AT04 would be more competitive than it proved in the first race in Bahrain.
“Engineers tell me we’re going to make some good progress,” he said. “But I don’t trust them anymore. I just want to see the lap times because that’s the only thing that matters.”
He continued: “During the winter months they told me the car was fantastic and we had made a lot of progress. Then we came to Bahrain and got nothing. What should I say?”
Asked on Friday in Miami whether he still abides by his earlier comments, Tost revealed that a key departure changed his perspective.
“As you can imagine, people I no longer trust are out,” he said. “And other guys I trusted, totally easy. They did a great job.”
Tost did not elaborate on which engineer he was referring to, and the team declined to provide any further details.
However, it is understood that AlphaTauri’s head of aerodynamics, Dickon Balmforth, left the Faenza camp after the start of the season.
Balmforth has been with the team since May 2018 and is based at their UK wind tunnel facility in Bicester.
Before joining Red Bull, he started his F1 career with Williams for three years from early 2003 to late 2005.
He worked for Adrian Newey’s aerodynamics team in Milton Keynes for over 12 years. He was promoted to chief aerodynamicist in 2014 before joining the sister company, then still known as Toro Rosso, in 2018.
Balmforth’s tenure with the team included Pierre Gasly’s memorable Italian Grand Prix victory in 2020 and other podium finishes.