Christian Horner admitted Red Bull was “highly nervous” about Max Verstappen’s ability to finish the Mexican Grand Prix as a result of Renault reliability issues.

After numerous problems for Toro Rosso throughout the race weekend, Red Bull opted to change Daniel Ricciardo’s power unit on Saturday in an attempt to avoid trouble in the race. However, Ricciardo was still one of four Renault-powered cars to retire, with only Verstappen and Pierre Gasly seeing the checkered flag.

Team principal Horner says an MGU-H failure appeared to be the cause of Ricciardo’s retirement and admits the number of cars being forced to stop made for a restless pit wall as Verstappen comfortably led.

“We made the difficult decision before the race to take the penalty with Daniel to avoid exactly the scenario that happened,” Horner said. “So when he went out with a completely set of new components on lap four or five, having had a fantastic couple of laps – he was at P7 right behind Kimi [Raikkonen] when it went – that was the first highly nervous moment, and then there were a few others as others dropped out.

“What we could do was manage the temperatures on Max’s car and keep them as cool as possible. So we turned the fuel flow right down – we built in so much margin that the temperatures were actually running as low as they were in Japan. He did a very good job of keeping everything under control.”

However, Horner played down his overall concerns about Renault’s reliability, believing the issues to be specific to the Autodromo Hermanos Rodriguez, the highest venue on the F1 calendar.

“This circuit seems to have caught them out. No doubt they will do some serious analysis to why they managed to get themselves on the back foot so badly here. Fantastic that we managed to win the grand prix but there have been an awful lot of failures during the weekend.”

The Red Bull team principal believes his team lost the chance of a double podium as a result of Ricciardo’s retirement, based on the early pace shown by the Australian.

“Daniel would have been at least third. He was right behind Kimi and looking in in great shape. He probably would have given [Valtteri] Bottas a hard time. It was a shame that we didn’t have both cars, but Daniel had a run of great luck earlier in the year. Unfortunately it balances itself out.”