Toto Wolff has confirmed Kimi Antonelli will start from the back of the field for this weekend's Italian Grand Prix after taking a new engine.
The world championship leader is set to exceed the limit of four power units that can be used across an entire season before incurring grid penalties.
Holding a 59-point advantage over team-mate George Russell in the Drivers' Championship, Mercedes feel the decision to take the grid drop in Monza is a necessary evil to aid Antonelli's chances of a maiden world title.
Mercedes could have only changed the internal combustion engine in Antonelli's W17, which would have resulted in a 10-place grid penalty, but Wolff insisted they will undergo a complete overhaul of the power unit.
The energy store and control electronics will also be changed, which are worth five-grid places each when exceeding their respective limits, and the FIA automatically assign you to the "back of the grid" when a driver has a 15-grid place penalty or more.
"Kimi will receive a grid penalty for replacing his engine and will start from the back of the grid. That's disappointing for him and for the fans who would like to see him fight for victory at the front at his home race, but our sport simply doesn't reward sentiment," said Mercedes team boss Wolff.
"When you make decisions that increase the chances in the championship, you sometimes pay a price for it in the short term. The goal is now clear: make up as many places as possible and get the maximum number of points."
The decision dampens Antonelli's chances of a home victory at Monza on Sunday, but the overtaking opportunities at the 'Temple of Speed' present the Silver Arrows star with ample chance to limit the damage of his grid drop.
Former Mercedes driver Valtteri Bottas showcased the advantage of a new power unit round Monza as he climbed from last place onto the podium during the 2021 Italian Grand Prix, and Antonelli will be hoping to cut through the field in the search of precious points.
Antonelli was able to extend his advantage at the summit following F1's return to action at the Dutch Grand Prix.
The Italian finished 11 seconds off the pace of race winner Lando Norris in the McLaren, but he finished ahead of his closest challengers Russell and Lewis Hamilton.
