Logan Sargeant has been put on notice at Williams - up your game or be ousted.
The American rookie struggled notably alongside teammate Alex Albon last year, but Williams team boss James Vowles has given him another chance for 2024.
But he required that Sargeant, 23, improve both his physical condition and his pace and consistency this season.
"He knows that what he was doing last season is no longer suited to the situation," Vowles said.
"We need to move up a gear. Logan needs to be the surprise of the season and put to good use the knowledge base he has spent 12 months accumulating.
"You can already see that in his body language and confidence, and now he has the opportunity to apply that knowledge on the track."