Norris starts 14 points adrift of Piastri so will re-take the championship lead for the first time since April if he wins the race and Piastri cannot make any ground.
Piastri has been struggling all weekend and although he looked to have saved his qualifying with a final lap that put him up to third briefly, others knocked him down as they benefited from the track improvement.
The Australian ended up 0.588secs off Norris’ pace to continue a difficult run of form in recent races.
Piastri said: “It all feels OK, just no pace. It is a bit of a mystery. It has been more or less the same gap all weekend. We will have to look at where it was going wrong then. Obviously a bit frustrating.
“This weekend, and last weekend really. It has just felt like the pace hasn’t come. Not 100% sure why yet. We will do some digging.”
McLaren team principal Andrea Stella said: “There is a little bit to review on Oscar’s side. [It’s] more difficult for him to use the car when the conditions are more sliding. A little bit like the conditions were in Austin.”
Verstappen, who has closed to within 40 points of Piastri after three wins and a second place in the past four races, was visibly struggling in the Red Bull – almost every lap he seemed to have an oversteer snap in the middle of the Esses, the quick series of left-rights in the middle of the lap.
“We tried a lot of stuff, even going into qualifying, and got it a little bit wrong in some areas of the track,” he said.
“You only need to look at the onboard [camera] and you see enough.
“All weekend we couldn’t find the grip in the car and it is something we need to understand, and when you have those issues you are sliding a lot and on this track you cannot afford that. This whole weekend has been tough.”
