Mercedes Formula 1 boss Toto Wolff says he is worried a frustrating 2018 campaign has taken its toll on Valtteri Bottas.

Bottas, who was forced to play a supporting role to teammate Lewis Hamilton’s championship bid after falling out of title contention himself following a difficult start to the year, finished a distant fifth place for the fourth successive race in the season-ending Abu Dhabi Grand Prix.

The Finn ultimately slipped to fifth in the drivers’ standings and became the first Mercedes driver since Michael Schumacher in 2012 to fail to win a race during a season, while Hamilton registered his 11th victory of the campaign at Yas Marina.

“He was really good until Baku,” Wolff told Channel 4.

“I think he would have won the race there without the puncture and he would have been in the lead of the championship.

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“After a long conservation I believe that when you have no shot anymore of the championship, and you know you need to give up, it kind of damages you mentally.

“I hope it’s not the case. He says not, he’s a strong Finn and a warrior but now over the winter we have to pick him up again and get him back to a good place.”

Bottas was forced into a two-stop strategy in Abu Dhabi after slipping behind Sebastian Vettel and Max Verstappen, having suffered a sudden drop-off in performance.

Wolff revealed Mercedes discovered an issue on the rear right brakes of Bottas’ W09, which he says instigated the second stop.

“On the pitstop something went wrong and when he went out we saw something was not right on the rear right brake, something was not perfect,” Wolff explained.

“We have data and it was a safety issue which is why we did the pit stop, so we don’t know whether there was a serious concern on the car that made the performance drop, or whether it’s just gone.”