After losing a power unit during his stoppage at Zandvoort, Hamilton is down to just two engines for the remaining six races of the 2021 campaign, one of which is a high-mileage unit.

Mercedes has conceded it has “question marks” over the engines remaining in its pool after being forced to fit a new power unit onto Valtteri Bottas’s car for the second race in a row at the Russian Grand Prix. 

It is expected that Hamilton will have to follow suit in moving onto a fourth power unit and subsequently triggering an automatic grid penalty. 

In an interview with Sky Sports F1, Mercedes boss Toto Wolff admitted that a strategic engine change at this weekend’s Turkish Grand Prix is a “possibility” for Hamilton. 

“Most important is that you don’t DNF because of a reliability issue,” Wolff said. 

“You can cope if it swings whether you finish second or third, I think that is OK. The championship is gonna go long.

“But if you don’t finish [it is worse]. So, we are looking at the parameters of the engines, making sure that we don’t suffer from any reliability problems.

“It’s a possibility. When and how it’s not yet decided.”

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Hamilton is two points clear of championship rival Max Verstappen, who took an engine penalty in Sochi and recovered from the back of the grid to finish second behind Hamilton. 

Asked if he is confident he can avoid another engine penalty this season, Verstappen replied: "We'll be fine with this engine to the end.”

Speaking after the race in Sochi, Horner stressed Red Bull cannot afford to “rely” on Hamilton taking a grid drop at one of the remaining rounds. 

“You’d assume the amount of Mercedes engines that are being changed in sister cars and customer teams, you’d maybe expect there to be a penalty,” he said. 

“But obviously we can’t rely on it.” 

And Horner is expecting the title race to go down to the wire and continue to swing back and forth between Red Bull and Mercedes. 

“I don’t think there’s any circuits that stand out as strongly as Russia and Monza, but for sure Mercedes will be strong,” he explained.  

“They won in Turkey last year, they’ll be strong there, but then we start getting Austin we should be there or thereabouts.

“Brazil, Mexico we’ve always been strong, we don’t know anything about Qatar, we don’t know anything about Jeddah.

“Then Abu Dhabi, you could say it’s 50-50 in what’s left on the table in what favours slightly one more team than the other.”