Red Bull "made a mistake" with their decision-making over Liam Lawson, says motorsport adviser Helmut Marko.
The New Zealander has been demoted from his position as team-mate to Max Verstappen following poor performances in the first two races of the season.
Lawson has returned to Red Bull's second team in a swap with Japan's Yuki Tsunoda.
Marko told BBC Radio 5 Live Breakfast: "His performance was unfortunately not good enough and that comes from self-confidence."
The 81-year-old Austrian, a key player in Red Bull driver decisions, said Lawson had "lost confidence and he couldn't show his real potential".