Helmut Marko says he does not regret letting Carlos Sainz Jr leave the Red Bull Formula 1 team's stable, because he does not rate Sainz as highly as Max Verstappen.
Sainz was backed by Red Bull throughout his junior career, and spent just under three seasons racing for its junior outfit Toro Rosso, and was then loaned to Renault at the end of 2017 and for the following campaign.
Renault opted against retaining the on-loan Sainz for 2019, and Red Bull's decision to promote Pierre Gasly instead of Sainz for the seat vacated by Daniel Ricciardo at the main team led to Sainz being released to join McLaren.
But while Gasly struggled to assert himself at Red Bull and was demoted back to Toro Rosso mid-season, Sainz flourished at McLaren, finishing the 2019 campaign sixth in the drivers' championship.
Asked whether he regretted that Sainz was allowed to leave, Red Bull motorsport advisor Marko told Autosport: "No.
"Sainz was comforted with one Max Verstappen [at Toro Rosso], and later we had to choose which one of the two to promote [to the main team in 2016].
"And when you get right down to it - Carlos is quick, we would not have signed him otherwise, but he is no Verstappen.
"We helped Carlos with his career and we didn't have to let him go. But we allowed the move to Renault and then to McLaren.
"We have a good relationship, but at that moment there was a Verstappen there, and there's a [performance] difference between the two."
Marko has previously been critical of the role Sainz's father, World Rally and Dakar champion Carlos Sr, played in his son becoming unsettled at Toro Rosso in 2017.
But asked whether the factor Sainz's 'political' father had played a part in the decision to release him, Marko said: "I wouldn't say he has a political father, rather one of those motorsport fathers who doesn't look at it objectively - which is understandable - and just always does what he thinks is best for his son.
"But it's not an isolated case, and by far not the worst."