Multiple Spanish sources are confirming the news, although they disagree about his chances.
Speculation says talks took place about forgiving Caterham's outstanding gearbox bills to Red Bull if Sainz, the latest cream of the energy drink company's junior programme, stepped in immediately to replace Kamui Kobayashi.
"Nothing is final, nor is it the only option," the newspaper quoted a source close to 19-year-old Sainz.
"Currently, Carlos is focused on this weekend's round of the Renault world series, and then we will talk and see."
The Spanish sports daily AS admits that a Hockenheim debut for Sainz was initially a possibility, but a deal between Red Bull and Caterham was not agreed.
"So now the intention of Red Bull is that Sainz will step into the Toro Rosso on a Friday this year, and next year he will be a race driver," the report said.