Ferrari's Charles Leclerc has been handed a potentially season-defining penalty by the FIA ahead of the Abu Dhabi Grand Prix.
Ferrari are in a battle for the Constructors' Championship with McLaren, and enter the final race of 2024 a total of 21 points behind their rivals.
The Scuderia were anticipating the Yas Marina circuit to be more positive for their car than Qatar, which saw them finish second and sixth.
And Leclerc topped the timesheets in first practice despite limited track time, underlining the car's pace.
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But the Monegasque driver spent much of the session pacing around his garage as Ferrari worked on his car - and the FIA have now confirmed the exact issue in giving Leclerc a devastating penalty.
He has received a 10-place grid drop for Sunday's race after exceeding his allocation of energy store components, meaning he can start the Grand Prix from no higher than 11th place.
If Leclerc does not finish in the points, McLaren would only need to collect six points to secure the title - though Ferrari will hope their driver can quickly climb up the field regardless of his starting position.
An FIA document confirming the component change reads: "The energy store used by Charles Leclerc is the third of the two new energy stores allowed for the 2024 Championship season and this is not in conformity with Article 28.2 of the Sporting Regulations."
The only driver to change components for this round is Fernando Alonso, though the Aston Martin driver is still within his allocation and has not received a penalty.
The Spaniard is unlikely to progress significantly in the race, though, as he described his Aston Martin as the 'worst car' during practice.
As for McLaren, Lando Norris finished second in first practice, two tenths behind Leclerc, in a potential indication of how close they could be to the Ferrari's pace during the weekend.
Ryan Smart