Lando Norris suggested he was held back in qualifying by the food poisoning bug that laid him low on Thursday despite claiming fourth for the São Paulo Grand Prix sprint.
The McLaren driver was in danger of missing Friday's running at Interlagos after staying away from the circuit the previous day due to sickness.
But fighting through the illness, the Briton managed to deliver to line up alongside George Russell on the second row and behind polesitter Kevin Magnussen.
"I feel a bit sick," conceded Norris. "I am really happy with [qualifying] to be honest.
"I don't feel good. I feel like I didn't do many things as well as I maybe should have done if I was feeling a bit better, but things still turned out really well.
"I think I was P1 in Q1, P2 in Q2. A surprisingly good day.
"Happy for KMag to see him on top, and how happy the whole team is. It is nice to see.
"Maybe not a perfect day."
McLaren fastest in early tricky conditions
Conditions were changeable throughout qualifying, with rain falling intermittently at only certain points of the race track.
On whether he could have asked for a better result, Norris explained: "When the conditions were a bit more tricky we were the quickest.
"But in the end, it was a bit more 'Do we take the risk and go out first when the track conditions are the best, or do we wait a bit and hope they get better?'
"We chose the second option, which really wasn't the correct one at the end of the day but I still managed to get P4 even with the wettest track out of everyone.
"You win some and lose some at the end of the day."