Kimi Antonelli has admitted that the pressure of being on the brink of the Formula 1 World Championship made him unusually tense during qualifying for the Mexican Grand Prix.

The Mercedes driver qualified fifth, 0.193 seconds behind pole winner Lewis Hamilton, but will start fourth because Max Verstappen has a one-place grid penalty. Ninth place or better on Sunday would guarantee Antonelli the title, regardless of what his remaining rivals do.

Antonelli said he was also still recovering from the illness that kept him away from his Thursday media duties.

I feel very tired — I still haven't recovered completely and it hasn't been an easy weekend, to be fair, he said.

"I've definitely been a bit more tense than usual, especially when you keep hearing, wherever you go, any time of the day, the same thing. And people telling me that it's already done, and knowing myself, I've been trying to block as much as possible this noise.

But it hasn't been easy, and definitely I've been a bit more tense today.

He was just one thousandth of a second slower than Lando Norris in final practice, but could not reproduce that form when it mattered. Antonelli said he felt reasonably comfortable on used tires in Q2 before struggling to put a lap together on a new set in Q3.

The 20-year-old also revealed that he had suffered a high fever and stomach problems earlier in the week. Although the worst of the illness has passed, he said the lack of energy contributed to mistakes during qualifying.

I'm aware that I haven't been driving well, he said. I was already going into qualifying and I didn't feel great, and I felt a bit low on energy. It's not an excuse, but for sure, it wasn't my finest.

His immediate remedy was simple enough.

I'm going to bombard myself with melatonin, so hopefully I will sleep a good 10 hours, Antonelli said. "I'm just going to try to relax as much as possible. My family has just arrived, so it's going to be good to have them here.

I'm just going to try to disconnect as much as possible, go to sleep, and then I'm ready for tomorrow.

Antonelli has a fresh set of tires available for the 71-lap race, although he expects Ferrari to have the stronger long-run pace. His first task will be to negotiate the long run to Turn 1 without becoming the central character in someone else's championship story.