Lauda, who knows his fellow-Austrian well, said Mateschitz had taken much more of a back seat than he had in the past as his two teams search for a new engine partner to replace Renault.
Champions Mercedes have said they do not want to supply a rival that could threaten their dominance but Lauda said Mateschitz had no real interest in them because of a historic dislike of the brand.
"I tell you simply, he does not do it," he said when asked at the Japanese Grand Prix whether the Austrian might make a fresh approach to Mercedes despite ongoing talks with Ferrari.
"Mateschitz at the moment, my feeling is he’s not pushing hard himself... he is not the leader like he was in the past."
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Asked whether he felt Mateschitz had lost interest, Lauda agreed: "It looks like it to me, yes," he said. "I've known him a long time and normally he’s the master of all this. But he never gets involved at the moment.
"It’s hard for me to say from a distance but the way Didi is acting at the moment, he could consider it (pulling his teams out)," he added.
Red Bull, drivers' and constructors' champions for four years in a row from 2010, have fallen out with underperforming Renault and are casting around for a replacement engine provider with Ferrari their only real option given Honda's woes.
However they have made clear they need a competitive engine if they are to stay in the sport.
"There is an option to stop F1. That is a scenario. If we don't have an engine that allows us to compete at the very front we will prefer to stop," Marko warned last week.
Horner has said Mercedes were approached at the British Grand Prix but recognised it was "always going to be a bit of a long shot" and Ferrari was the main focus.
Lauda felt however that Mateschitz was never really serious about doing a deal with the German carmaker.
"I know the reason. He doesn’t like Mercedes. I know him very well. So Ferrari is his option now and it’s up to him whether he wants to take it or not," he said.
(Reporting by Alan Baldwin, editing by Ken Ferris)
