Niki Lauda senses that Red Bull owner Dietrich Mateschitz has lost interest in Formula 1, that it could prompt him pulling his teams out.
Red Bull has made clear in recent weeks that it will not continue in F1 if it is unable to secure competitive engines.
Its hopes of getting a deal with Mercedes have fallen through, and the Milton Keynes-based team's talks with Ferrari have not moved forward as quickly as it had hoped.
Lauda, who is non-executive chairman of Mercedes, suggests that the clearest sign of Mateschitz's mindset is that he has not been involved in a push to secure the right engines as he would have done in the past.
"He doesn't do it – he simply does not do it," explained Lauda. "Mateschitz in the moment, my feeling, is he is not pushing hard himself.
"He lets Helmut [Marko] and Christian [Horner] work on it, but he is not the leader like he was in the past. In the past he did everything himself."
When asked if he believed Mateschitz had lost interest in F1, Lauda said: "It looks like it, yes, because I know him a long time and normally he is the master of this and he never gets involved at the moment."
Risk of quitting
Red Bull has been open that the threat of it pulling out is real, and Lauda says that Mateschitz's behaviour means there is a big chance of it happening.
"It is hard for me to say from a distance, but the way Didi is acting at the moment, he could consider it," said Lauda.
"Because to end up in that situation where there is only one engine available is tough."
No proper approach
Mercedes decided at the Italian Grand Prix that it would not supply Red Bull with engines for 2016, amid concerns about the competitive impact of its own outfit.
Lauda has also revealed that there was also never any proper approach from its rival about a power unit deal.
"There was a long discussions we had internally but we never got approached properly if he [Mateschitz] wants the engine.
"We don't have to go around and back people to use the engine, [it should happen] the other way around. So we were never approached and never thought about it."
He added: "If I am not approached, what should I do? Throw the engine at him as a gift? It doesn't work like this.
"And there is a reason. I know the reason. He doesn't like Mercedes. I know him very well, so Ferrari is his option now and it is up to him if he wants to take it now."