A clear favourite has emerged to be Daniil Kvyat's teammate at Toro Rosso next year.
Earlier, the top favourite was Dan Ticktum, but following controversial comments about Mick Schumacher, Red Bull's top brass say the Briton now needs more time.
Pascal Wehrlein was thought to be in the running after skipping out of his Mercedes contract, but he has now signed up for Formula E.
And Mick Schumacher, despite winning the European F3 championship and qualifying for a F1 super license, is expected to spend at least a year in Formula 2.
"I could drive in formula one, that's clear," he told the German broadcaster Sat.1. "It's still my big goal but it's still very unrealistic.
"In order to be 100 per cent prepared to be there as a full race driver, it's necessary to go through all the different series of formulas," 19-year-old Schumacher added.
As reported recently, the new favourite is Alexander Albon, a British F2 and Formula E driver with a Thai heritage who has historical links with Toro Rosso owner Red Bull.
The 22-year-old is believed to be the subject of current negotiations between Red Bull and Nissan, the Japanese manufacturer with a multi-year Formula E contract with Albon.
