Red Bull consultant Helmut Marko has admitted he can't explain why Daniil Kvyat's time with the team did not pan out following his departure.
Having been billed as a future world champion by Red Bull, the Russia managed to earn a swift promotion from feeder team Toro Rosso to Red Bull Racing back in 2015.
However, the Kvyat struggled after making the step up, failing to match the pace of his Australian team-mate Daniel Ricciardo while a series of high-profile accidents also hindered his progress.
Kvyat was eventually demoted back to Toro Rosso and was allowed to leave the Red Bull family at the end of 2017 and has since gone on to sign up with Ferrari in the role as development driver.
Marko was disappointed they could not get the most out of Kvyat but feels the diver was given enough chances.
"Unfortunately we don’t know why," Marko said. "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."
Meanwhile Ricciardo is 4001.00 to win the 2018 World Drivers' Championship, while team-mate Max Verstappen is 2001.00 to take the title.
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