Dr Helmut Marko admits it is not "100 percent certain" that Sergio Perez will still be in a Red Bull car in 2024.
Kleine Zeitung newspaper in Austria is reporting that, during Formula 1's August break, Daniel Ricciardo travelled to Graz to catch up with Marko.
That is despite the fact that Mexican Perez is already signed up for 2024.
"Nothing is 100 percent certain in Formula 1," Marko told the newspaper when asked whether Perez has a job guarantee for next year. "It just doesn't exist.
"There are always performance-related situations somewhere that need to be discussed. We'll take a look and discuss how to proceed in Zandvoort, then we'll know more," the 80-year-old added.
After losing his McLaren seat due to poor performance at the end of last season, Ricciardo returned to F1 as Red Bull's reserve driver this year - and just prior to the summer break, replaced Nyck de Vries at Alpha Tauri.
The Australian, 34, is dating Heidi Berger - the daughter of well-known Red Bull confidante Gerhard Berger.
Together, Heidi and Ricciardo travelled to Kitzbuhel for holidays - and then had a meal with Marko in Graz.
"We saw each other," Marko confirmed. "That's clear when he comes to Graz.
"He (Ricciardo) has a very positive personality, a successful career and incredible experience. His momentum and vigour caused a real jolt at Alpha Tauri. It was a real boost of motivation," he said.
It is clear that, if nothing else happens, Ricciardo will be offered another season at Alpha Tauri next year.
"There will be a major update at Alpha Tauri and we will see whether the direction is right," said Marko. "A driver like Ricciardo will of course help enormously as he tells you exactly what is good and which updates are useless."
