Lewis Hamilton is to stand aside for Nyck de Vries for FP1 at the French Grand Prix.
Each team is required to use two first practice sessions for rookie driver runs throughout the season as F1 aims to bridge the gap between junior formulae and the highest echelon.
Mercedes has elected to complete its first run of the season at Paul Ricard this weekend, with Formula E and former F2 champion de Vries taking charge of the W13 on Friday.
It means Hamilton will step aside for an hour on a weekend the Silver Arrows are expected to perform well, given the smoothness of the track surface at the French venue.
"Nyck is replacing Lewis in first practice this weekend as part of the allocated sessions for young drivers this year.," confirmed team principal Toto Wolff.
"So, we're looking forward to seeing how he gets on."
De Vries has already completed a young driver run this year, driving the Williams FW44 during first practice at the Spanish Grand Prix.
Head of vehicle performance at Williams, Dave Robson, said after the run: "He has what he needs to be a top-quality competition driver.
"He is worthy of a place on the grid I think but so many people are. He took his opportunity well and he should be pleased and proud of what he did."
The Dutchman sits eighth in the Formula E standings with four rounds left after enduring a season filled with misfortune.