Red Bull team principal Christian Horner says Naoki Yamamoto "doesn't fit the criteria" for a race drive at his team or Toro Rosso.
Yamamoto debuted in Formula 1 with a run at Toro Rosso in the first practice session for the Japanese Grand Prix.
The Super Formula champion was just a tenth adrift of Daniil Kvyat in matching machinery and certainly looked the part around a Suzuka circuit he knows well.
At 31-years-old, Yamamoto's profile differs from the younger talents Red Bull tend to look for, although he has been tentatively linked with a race seat at Toro Rosso, where the line-up has been volatile in recent years, while influence from Honda could also be a factor.
"He's done a very good job for his first session in a Formula 1 car," Horner told Sky Sports.
"I think he acquitted himself extremely well. He's had a very successful career racing over here and with Jenson [Button] in the GTs. He doesn't fit the criteria [for a race seat at Red Bull or Toro Rosso] at the moment, but he's certainly worth giving a run and having a look at today."
Horner saw no reason to doubt that Yamamoto's ability to match Kvyat had nothing to do with a technical difference between their cars.
He said: "I don't know the ins and outs of their run plan, but it's pretty usual they run a standard setting across the cars so he's done a good job there."