Red Bull motorsport boss Helmut Marko still has one F1 seat available at Toro Rosso, but it won't be filled by McLaren's departing driver Stoffel Vandoorne.
The 26-year-old is out of a drive for 2019 and had initially eyed a spot at the Faenza-based outfit and Sauber when he was told of his fate by McLaren boss Zak Brown.
Marko declined to take on the Belgian however, believing his level of talent isn't good enough to succeed in F1, a painful appraisal given Vandoorne's success in the lower formulae before his difficult stint with McLaren.
"We will not take Stoffel," Marko told Belgian broadcaster RTBF. "I think he's just not fast enough for F1!"
Mercedes boss Toto Wolff offered a more nuanced opinion of Vandoorne, suggesting Mercedes could even throw him a lifeline in the not so distant future.
"I have always liked Stoffel, a brilliant driver in the junior categories," said Toto Wolff.
"We must now try to understand why it did not work for him in F1, but maybe there could be some news about him soon.
"I think his character and speed would work very well at Mercedes, but for now we will have to see," added the Austrian.
Wolff was likely referring to Mercedes' involvement in Formula E through its link with German team HWA, the manufacturer's official representative in the all-electric series for its 2018/19 season.
HWA will announce its driver line-up on October 8, with in-house driver and Mercedes-supported racer Gary paffett expected to be named as one of the team's drivers.