What happened: George Russell said Mercedes' car is still short of the mark after opening the Bahrain Grand Prix weekend in Malaysia with a major upgrade. He flagged pressure from Max Verstappen and McLaren after a difficult start on Sepang's hot, abrasive surface.

Why it matters: That leaves Mercedes with setup work to do before qualifying on a circuit where tyre degradation can erase any gains from new parts. The concern lands just after Mercedes brought a new floor and sidepods to the Bahrain GP in Malaysia, raising the stakes on how quickly the package can be switched on.

What to watch: Final practice and qualifying will show whether Mercedes can widen the car's operating window before parc ferme. Russell's longer-run pace against Red Bull and McLaren is the next clean read on whether Friday's concern carries into the race.