Sainz is one of 10 F1 drivers out of contract at the end of this season, and there will be an increase on the supply and demand side with Audi entering a team in 2026.
Their rush to secure drivers ahead of time might have forced Red Bull's hand, but team boss Helmut Marko has dismissed that notion as nonsense.
Advantage Perez
"The driver market has exploded in April, and normally no one talks in April," he told Motorsport.com. "It is ridiculous, but we won't jump into this game ourselves. We will wait and see, and only then make the best choice later on.
"I don't know what is going on. I have heard that Audi is making pressure, but it is a little bit strange for a newcomer to make pressure on the driver market."
Audi might be tempted to make move for Sergio Perez, champion Max Verstappen's partner at RBR and another one of those drivers whose contract is expiring.
But the Mexican is currently second in the drivers' standings after earning a 1-2 with Verstappen at last Sunday's Japanese Grand Prix, and team principal Christian Horner has hinted there is no need to turn to the market.
"We're not in a huge rush," he said. "And, obviously, there's a significant amount of interest in our cars, as you would expect. But Checo has the priority, and it is going to be a few more races yet before we start to think about next year."