McLaren figures have been left red-faced after being outperformed by their old Honda engines in Bahrain.
Newly Honda-powered Toro Rosso’s Pierre Gasly will start the race from an impressive fifth on Sunday — while Fernando Alonso did not even make the ’Q3’ qualifying segment.
Stoffel Vandoorne was even slower, and both were also behind the other Toro Rosso driven by Brendon Hartley.
"I have no explanation. Obviously we have not done a good enough job," said Vandoorne.
Fernando Alonso played down the significance of McLaren’s ongoing troubles in the wake of the Honda divorce.
And earlier, boss Eric Boullier had said McLaren’s next goal is the top three teams.
"It’s ambitious, but from time to time we should be able to fight with Ferrari and Red Bull," he said.
But after qualifying, the Frenchman said he was "surprised" and ordered a "big investigation" back at Woking.
For the entire Red Bull camp, however, Saturday’s results were a major boost.
Red Bull Racing, who like Toro Rosso are also owned by the famous energy drink company, is openly considering a switch from Renault to Honda power for 2019.
"The team obviously has the opportunity to move to another engine. That’s no secret," said Daniel Ricciardo, who is linked with a move to Ferrari for 2019.
"It’s natural that if Toro Rosso continues to do so well, it will reassure Red Bull and the likelihood will be higher. I’m watching, but as drivers we’re not involved in the discussions," he added.