Christian Horner admitted it was a bittersweet afternoon for Red Bull after Daniel Ricciardo clinched pole while Max Verstappen was forced to sit out the all-important qualifying session.
A big mistake by the Dutchman in the morning's free practice resulted in a heavy contact with the barriers and a scramble by his crew to ready his damaged RB14 for qualifying.
Alas, as the final preparations were taking place, an ominous sign was identified when the car was fired up.
"Basically the car was fired up, but then we saw an oil leak in the gearbox, and that was it," explained Horner.
"They did their best to try and get the gearbox replaced, which would have been a five-place penalty.
"I have to say, both car crews - Daniel's crew as well steaming in - doing everything they could to make it happen but today unfortunately it wasn't to be," lamented the Red Bull team boss.
It was a heavy blow for the Milton Keynes-based squad which has been performing comfortably above its rivals in Monaco, and one that leaves Verstappen with the massive challenge of starting Sunday's race from the back of the grid.
Horner is confident however that the 20-year-old will take away a valuable lesson from his blunder and the lost opportunity.
"This place bites and he got bitten pretty hard today in a session that doesn’t really count for anything, other than setting the car up," said Horner.
"He’s in a car that’s capable of winning this Grand Prix and that will hurt him even more because you don’t get that many opportunities to win a Monaco Grand Prix.
"He knows that more than anybody and I would imagine that was a pretty painful qualifying for him watching what could have been.
"There's no more brutal lesson that what he's just had. I'm sure that he's smart enough to hopefully learn from that."
At the end of the day however, it was all about mixed feelings in the Red Bull camp.
"It feels a little bittersweet. Really delighted with the pole but we should have had two cars up there," admitted Horner.
"It's frustrating with such a fast car bot to have both cars on the front row of the grid."