Jenson Button fears McLaren will overtaken by "everyone" on the Yas Marina straight because of the limitations in Honda's power unit.
The McLaren driver finished Friday's practice in Abu Dhabi down in 16th place, a full two seconds off the pace.
However, it is the team's speed down the straight that worries him the most.
"The race is going to be very tough," he told Autosport. "Our deployment is stopping really early on the straight.
"You're sat there waiting for everyone to overtake."
The Brit, though, is set to make changes to his car overnight.
Team-mate Fernando Alonso managed to slide into the top ten on his super soft tyre run leaving Button to deduce that there is more to come.
"We were trying very different things today, very different set-ups," he said.
"It's all about understanding for next year. I'll be changing my car tomorrow quite a bit.
"I normally enjoy driving around here but today wasn't so much fun.
"We know what to do tomorrow to make it more enjoyable."