Mercedes boss Toto Wolff says that Sebastien Vettel's temperament let him down in the 2017 Formula 1 world championship battle.
He said that underneath Vettel's cool exterior lay a much more emotional and passionate core than most people realise.
"This has made him win championships in the past," Wolff told BBC 5 Live's Formula 1 review show. "This year, it has let him down.
He pointed to the infamous moment in Baku when the Ferrari driver intentionally banged wheels with Lewis Hamilton's Mercedes as proof.
"Sebastian's emotion and anger just ran away with him in that moment. He would be the first one to acknowledge if he could turn back time, he wouldn't do it again."
At the time, Vettel believed that Hamilton had been 'brake testing' him behind the safety car before the restart. But reviews of car telemetry showed this hadn't been the case.
"We immediately looked at the data to see whether you could see something like a brake test," Wolff confirmed. "And we couldn't see any of that."
Wolff said that Vettel's hot-headedness was also to blame for the three-car crash at the start of the Singapore Grand Prix. Vettel's attempts to stop Max Verstappen overtaking into turn 1 saw them collide with Kimi Raikkonen.
"I don't know whether it was pressure or not," said Wolff. "[He needed] to lead the race after the start. He tried to come in strong, and with the lack of visibility in these cars he just triggered a chain reaction.
Compared to Vettel's rashness, Wolff said that Hamilton had been driving better than ever this season.
"Lewis by contrast has grown as a personality," he suggested. "As a driver and outside the car and that made him very strong."
Mercedes will need that sort of advantage again next season if it's to keep hold of the drivers and constructors championships.
"The longer a regulation stays stable the more everybody closes up," Wolff explained. "For me it was already pretty close at many races [in 2017]!
"It is going to be an even more tough fight next year against Red Bull and Ferrari." He added that the team was working hard to remove some of the current car's 'diva' qualities next year.
"Having said that, every car has a certain DNA," he said. "I don't think you want and will have a car that is strong on 21 circuits next year. But in the end it has to be strong on most circuits."
Gallery: The beautiful wives and girlfriends of F1 drivers
Keep up to date with all the F1 news via Facebook and Twitter
