Vettel and Ferrari are to part ways at the end of this year, ending what will have been a six-season association.
While Vettel has stated he is to consider his options for the future, Ferrari is wasting no time in bringing in his replacement, with McLaren driver Sainz set to partner Charles Leclerc at the Scuderia for 2021.
The 25-year-old Sainz has enjoyed a strong career in F1 to date after initially cutting his teeth at Toro Rosso, spending over two and a half seasons with the team but finding his way blocked to promotion to Red Bull by the Max Verstappen/Daniel Ricciardo partnership at the time.
Late in the 2017 season, Sainz was offered the chance to join Renault as a replacement for Jolyon Palmer, one which he grabbed with both hands as he signed on for the 2018 campaign with the French manufacturer, only to be pushed aside to make way for Ricciardo.
Sainz, though, then found a home for last season with a McLaren team on the rise, and although it is an organisation where he has been made to feel wanted and appreciated, it appears as if he has unsurprisingly been unable to resist the lure of a seat at Ferrari.
The Spaniard's results throughout were superb, notably claiming his debut podium in Brazil - albeit following the race after Lewis Hamilton had been handed a penalty - helping McLaren to finish fourth in the constructors' championship, the team's best placing since 2012.
From Ferrari's perspective, Sainz represents a cut-price option compared to the apparent €35million-per-year salary of Vettel, and the high income that would have been demanded by Ricciardo.
It is also felt he will be able to form a positive partnership with Leclerc, notably after witnessing the bond formed with Lando Norris at McLaren in 2019.
Sainz's father, Carlos Sr, while conceding his son "is happy where he is", added in an interview with Movistar+: "It is true that things have moved a lot lately.
"I want to think that sooner or later there will be a solution because we cannot wait another two months or more going with these rumors and these stories.
“I cannot tell you anything more because it is a delicate situation.”
Sainz Sr is confident his son could make the step up to Ferrari. He said: “Life happens, and either you stagnate or you take steps.
"From what I see as a father, he has the ambition to continue to improve, to take steps forward as he did last year.
“That has to be the philosophy of any athlete, and all I can do is encourage him to do it.”
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