Red Bull team principal Christian Horner feared a gearbox problem on Daniel Ricciardo's car could have forced him into an early retirement from Sunday's Singapore Grand Prix.
Ricciardo finished in runner-up spot for the third successive race in Singapore, having avoided opening-lap carnage to move into second place behind Lewis Hamilton. While Red Bull looked to be faster than Mercedes throughout the weekend, Ricciardo was ultimately unable to challenge Hamilton for victory.
Horner revealed after the race that his team was concerned about whether the Australian could even make half-distance after encountering a significant amount of oil pressure in the gearbox of Ricciardo's RB13 early on.
"Even before the first Safety Car we could see an awful lot of oil pressure in the gearbox and we were thinking 'crikey, this is only going to go until about half-distance'," Horner told Sky Sports. "Daniel had the instructions to start managing that and of course he then had to sacrifice a lot of lap time to do that.
"He did that incredibly well and managed to nurse the car home for another hour and a half. We were so focussed on the issue Daniel was managing it was just a question of getting the car to the finish."
When asked if he felt Ricciardo could have won without the issue, Horner replied: "He would have certainly been closer and able to have put some pressure on but I think it was very different conditions today with the rain, with the rubber gone. It was cooler as well. Mercedes, and particularly Lewis -- I think we had Valtteri [Bottas] covered -- but Lewis had a really strong day."
Ricciardo said he was forced to short shift for the rest of the race in order to manage the problem, but insisted the gearbox issue was not the fundamental reason as to why Red Bull was unable to claim its second win of 2017.
"I'm not too sure what the issue was but I was advised to do some short shifts from fairly early in the race and then I was reminded to continue to do that until the end," he explained. "There were some issues going on and that was the way to manage it. But ultimately it didn't change shape of race. That wasn't reason we were second and not first."