Red Bull was a "tough" environment for Carlos Sainz to thrive in, according to McLaren supremo Zak Brown.
Sainz, now 25, made his debut via the Red Bull junior program, racing for Toro Rosso for three years until 2017 before switching to Renault and finally signing a contract with McLaren that began in 2019.
"Carlos has been outstanding with us," Brown is quoted by Spain's Marca sports newspaper.
"I think he had one-year contracts in the Red Bull-Toro Rosso environment," he explained. "Obviously Red Bull is a fantastic team, but they can be tough with their drivers.
"I think Carlos is a driver who needs to know that he has a team that supports him and that the next race will not be the last for him. That is a little of the sort of atmosphere they (Red Bull) sometimes create."
Brown is also happy with McLaren's other driver, Lando Norris, who made his F1 debut with the once-great British team last year.
"It was a risk, as Lando was the youngest British driver," said Brown.
"But from his first free practice he was impressive. Even when he ran the Daytona 24 hours with Fernando Alonso there was a debate to see which was the fastest.
"Lando took on the challenge but I knew he was ready when he did his first practice. He was as relaxed as when I saw him on the grid of a Formula Renault race," he added. "He seemed calm and immediately had the speed."
