It was Mercedes' Valtteri Bottas that was the cause of the yellow flag, as the Finn hit the barriers on his final run in the session. It was a hefty crash, with the impact measured at 17G meaning that the medical car was automatically deployed.
Bottas was unhurt, but the incident meant that the drivers had to back off and abort their laps. Due to this, Vettel originally qualified in third, but will move up to second due to Verstappen's three-place penalty.
Vettel was not overly pleased with his session, seeing it as a missed opportunity for his Ferrari team.
“It’s not ideal with the yellow flag otherwise I think it could have been a better session for myself," Vettel said after the session.
“I had it in my hands in the first run, I was probably too cautious after a good first sector, then I lost the rhythm, and I was too aggressive in the end, had a big snap in the first corner.
“I was quite confident I could make up some time. There was a yellow flag, but it happens. I think we could have matched Max’s time, but would, could, should.”
The four-time world champion went on to say that he believes tyre wear will be a defining aspect of Sunday's race, with strategy the key to a good result.
“The key tomorrow will be to have a good race car to look after the tyres, to choose the right strategy.
“We all start on the same tyre, but I think it will be a close race. Mercedes – I don’t know what happened to them today, but tomorrow they will be quick.”
Ferrari has not won in Mexico since the track was added back to the calendar in 2015, but with a front row lockout and the best straight-line speed the Scuderia are in good shape to break that trend.
Bahrain International Circuit - Winter testing