Lewis Hamilton believes overnight changes made to his Mercedes car placed him on the back foot during qualifying in Las Vegas.
Hamilton suffered his third Q2 exit of the season in the early hours of Saturday morning as he could only manage the 11th quickest time.
The seven-time World Champion was joined in the drop zone by Red Bull's Sergio Perez.
However, Hamilton is set to start the race from 10th due to a grid penalty for Ferrari's Carlos Sainz.
The sole representative practice session on Friday morning saw Hamilton end up in ninth place, but the 38-year-old has asserted that his car went in the wrong direction as the weekend progressed.
“There are always differences,” Hamilton told media including RacingNews365.
“I just struggled. [During practice] I was feeling better, and I was more competitive. And then we made some changes overnight and it didn't feel great today.
“So this car is a bit on a knife edge. The track is fun, but I'm sliding around a lot. But the race is going to be really interesting. A lot of work to do from 11th.”
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Hamilton expecting high tyre degradation
Last time out at the Sao Paulo Grand Prix, Mercedes suffered heavy degradation during the race which limited its pace during the race.
With the cars set up for optimal straight-line speed in Las Vegas, Hamilton is expecting another race of heavy degradation in Las Vegas.
“We're all on low wings,” he said. “So there's going to be a lot of degradation. There may even be more degradation than we know.
“No one has driven the Hard tyre yet. Max [Verstappen] has two Hards and two Mediums, we have one medium and two Hards.
“So it's going to be a long race, it's going to be about managing degradation.”