Red Bull team principal Christian Horner has revealed a refuelling issue cost Sergio Perez a shot at pole position for Sunday's Azerbaijan Grand Prix.
Perez was held in the garage by his team ahead of the final hot-lap in the top-10 shoot-out around the Baku City Circuit, leaving team-mate Max Verstappen to question why he was being sent out first ahead of the Mexican.
The delay for Perez denied him a potential tow in the dying stages, although he still managed to claim second on the grid ahead of Verstappen, albeit three-tenths of a second adrift of a staggering pole lap from Ferrari's Charles Leclerc.
Explaining what unfolded, speaking on Sky Sports F1, Horner said: "There was a small issue with the refuelling that just delayed him, unfortunately. It was just a numbers error.
"It was a shame for Checo because he didn't get the benefit of a tow but then he did have a perfect out lap, and you could see his performance was pretty mighty.
"With a tow, it would have been close but I still don't think we would have quite had the pace to have nailed Charles.
"But a great performance from both the guys, with Checo carrying that performance from Monaco at a track he has always excelled at here, and without the benefit of any tow. A good lap from him."
Red Bull has edge on race pace?
Red Bull has so far proven this season it often has a better race car than over one lap, with the speed trap highlighting the RB18 is nine kilometres per hour quicker than the SF-75, which will prove key for overtaking.
"I thought before quali it was going to be very tight," added Horner. "I felt over a single lap Ferrari had the edge, but on Sundays this year we've had a good and competitive race car.
"At a track you can overtake at, hopefully, we can give them a hard time tomorrow.
"It's such a long straight here and the DRS effect is pretty powerful. Of course, you've got to be close enough in the middle sector to use that so it will all be about trying to go with them, convert the start.
"We've seen this year some great racing between ourselves and Ferrari, and this year's cars have demonstrated you can follow a little closer and overtake, so we will be hoping to make use of that for tomorrow."