Red Bull Racing team boss Christian Horner is surprised that competitor Mercedes is struggling with the reliability of the engine.
The Briton thinks any problems with the German team could play a key role in the battle for the world title.
On Friday it was announced that Mercedes driver Valtteri Bottas will receive a new combustion engine and will have to take a five-place grid penalty for the Grand Prix in the US.
Sebastian Vettel (Aston Martin) and George Russell (Williams), who drive a Mercedes power source, also have to have their engines replaced.
"The reliability issues could play a key role in the title race," Horner said Friday after the first two practice sessions in Austin according to
Autosport.com
.
"Certainly now it is important to last until the end of the race, so reliability can be decisive."
The big question is whether Lewis Hamilton also needs a new engine.
Max Verstappen's competitor in the battle for the world title received his fourth combustion engine of the season at the previous Grand Prix in Turkey and received a grid penalty of ten places.
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Verstappen calls Hamilton 'stupid idiot' during training in US
'Unusual for Mercedes to struggle with reliability'
If the seven-time world champion gets another power source in his car, he will have to go back five places in the starting grid.
Hamilton is already six points behind Verstappen in the World Cup position, so a new grid penalty would be bad for the Briton.
"It's very special to see Mercedes struggling with the reliability of the engine," says Horner.
"For the past six or seven years they have set the tone in that regard. It is unusual for them to be in this situation now."
The Red Bull team boss hopes that Verstappen, who got a new engine in the Russian Grand Prix, can finish the season with his current power source.
"That is our assumption. By taking a grid penalty in Sochi, we have put ourselves in a better position again. But the situation can change quickly."
The United States Grand Prix starts on Sunday at 9 p.m. (Dutch time).
After this race, there are still five Grands Prix on the program this season.
United States GP times
Third free practice: Saturday 20:00
Qualification: Saturday 11 PM
Race: Sunday 9 p.m.