Red Bull has traced the cause of Max Verstappen's mechanical failure in FP2 to a hydraulic issue, a cause which should not have a bearing on the remainder of the Dutchman's race weekend.
Verstappen and Daniel Ricciardo were sitting pretty all day on Friday, dominating both free practice sessions with a comfortable margin over their rivals.
However, the Red Bull camp was put an high alert when Verstappen pulled off to the side of the track in the closing stages of qualifying, his RB14 the victim of a suspected hydraulic failure.
"It's a hydraulic issue of some sort, so we need to get the car back to understand what's caused it," Horner told Sky.
"Then if it is an engine change, he's still got one in his pool, so he should be alright. But we need to get the car back first of all to understand it."
The impressive form of Carlos Sainz and Nico Hulkenberg, who both ran consistently among the top 5 on Friday, validated the good performance of Renault's engines at Mexico City's high altitude venue.
"What's happened here, as I said before the event, this high altitude tends to even things out a bit," explained Horner.
"The engines are struggling for air, the brakes, the cooling, everything is struggling for air mass through here.
"We're able to run the car in its optimum state [high downforce] and we've got a power unit that looks competitive relative to the others."
Red Bull's comfortable advantage could be short-lived however, according to Ricciardo, who believes that both Mercedes and Ferrari will reduce the gap to the bulls on Saturday.
"The low fuel pace looked good, so I am relatively happy with the car low fuel, high fuel not so competitive so we have some work to do there," said the Aussie.
"I am relatively happy, but I don't want to be naive though. I think Ferrari and Mercedes will give us a push tomorrow."
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