Lewis Hamilton admits he found it difficult to remain at the same level of competitiveness in the final races of 2017 having already clinched the Formula One world championship.
Hamilton sealed his fourth world title in Mexico, but failed to claim victories in either of the final two races of the campaign in Brazil and Abu Dhabi. A crash in qualifying forced Hamilton to start from the pit-lane at Interlagos, while he was unable to find a way past Mercedes teammate Valtteri Bottas in Sunday's finale at the Yas Marina Circuit, having been pipped to pole position by the Finn.
In 2015, when Hamilton won his third world championship title with three races to go, he was beaten to victory by teammate Nico Rosberg in all the remaining grands prix.
"I have tried my hardest to stay on it but I wouldn't say it was 100% of what it was while in the season," Hamilton said. "You want to enjoy it. I do still try and turn up and do the job but it's not so easy.
"It's clear that something happens once you've won the championship. All I can say is that in the week after I won the championship, I partied a lot. That's what you do. I didn't do that before the other races.
"The energy has not been the same, even if I have approached the races the same. But I'm not worried about that. Next year it will go back to what it was in the second half of the season."
But Mercedes boss Toto Wolff said he had not seen anything to suggest Hamilton has suffered a dip of form or drop off in commitment.
"He is somebody who is very diligent in progressing," Wolff explained. "I don't think 2015 has happened. He had an accident in qualifying that happened after he has won the championship. And where that comes from I don't know.
"These guys are pushing the cars to the limit. He didn't put a foot wrong all season. I'd rather it happened after the championship than before. Here he looked very good until qualifying and then Valtteri put it all together and I think you just have to acknowledge this was Valtteri's weekend."