Dr Helmut Marko has admitted Nyck de Vries may no longer be in the Alpha Tauri cockpit by the time Formula 1 reaches Zandvoort.
Zandvoort, the first race after the August summer break, would be the struggling Dutchman's first home Formula 1 event.
But there are rumours 28-year-old de Vries has only been given until the start of the summer break, to take place after the forthcoming Hungarian and Belgian GPs, to up his game.
When asked if the Dutchman will still be in the Red Bull-owned car at the Dutch GP, Marko told Viaplay: "When is the race in Zandvoort?
"I can answer you as soon as we get to Zandvoort," he added at Silverstone.
There are rumours Daniel Ricciardo, Liam Lawson, Ayumu Iwasa and Alex Palou are among the contenders to replace de Vries.
"We are reviewing the situation," Marko, a top Red Bull executive, admitted.
"It's no secret that Nyck hasn't delivered what is expected of him. It's a hard sport and we have to always be looking to the future.
"We are evaluating his performance, and if necessary, we have to make decisions."
The apparent demise of de Vries' Red Bull-Alpha Tauri adventure would open up a spot in the Red Bull program - and Marko already has his eye on a potential new member.
He is Pepe Marti, an impressive 18-year-old Spanish driver who is managed by Fernando Alonso's A14 management company.
Marko met with Marti at the Spanish GP, and they were again photographed together in the Red Bull motorhome at Silverstone on Friday.
"For me it was a shock," said Marti recently, "because in the end you're waiting your whole life for someone from F1 to pay attention to you."
Marko confirmed: "He is very young and he is doing very well. Yes, he is a possible signing for our academy."
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