Red Bull Formula 1 advisor Helmut Marko remains unsure what sparked Daniil Kvyat's dramatic downturn in form that led to his eventual dismissal from Toro Rosso earlier this year, saying it was something that the team "could not cure".

Kvyat enjoyed a solid first year with Red Bull's senior F1 team in 2015, beating the highly-rated Daniel Ricciardo in the final drivers' standings, but was demoted back to Toro Rosso after four races in 2016 to make way for Max Verstappen.

Kvyat was benched twice through 2017 at Toro Rosso due to poor form, with his final dropping coming after the United States Grand Prix in October, leading to his eventual exit from the Red Bull motorsport programme.

Asked in an interview with the official F1 website why Kvyat cracked under pressure, Marko said: "Unfortunately we don’t know why. Maybe because of that we couldn’t cure it.

"In his first year in F1 he was a revelation, often being quicker than Ricciardo - that’s why we moved him to Red Bull Racing. But then suddenly his curve started to run south. This happens sometimes unfortunately.

"We gave him more than one fair chance, but he could not use his potential.

"That’s how it sometimes goes."