Nico Rosberg claims that inconsistency is Lewis Hamilton's one weakness, according to the former Williams and Mercedes driver.
The 32-year-old German, who retired last year after pipping Hamilton to the title prior to his retirement, believes that the Brit has his flaws, despite leading the Drivers' Championship by 59 points.
Hamilton extended his lead at the summit of the standings after claiming an eighth Grand Prix of the season in Japan on Sunday.
Speaking to Sky Sports, Rosberg said: “A little bit of a weakness is some ups and downs.
“Not quite 100 per cent consistency.
“Vettel has a clear edge in terms of consistency and maybe in terms of race speed, ever so slightly.”
Hamilton's triumph on the Japanese circuit came after Sebastian Vettel's engine failed, and following the win, he could clinch his fourth title at the US Grand Prix, should he finish top of the podium, and Vettel finishes outside the top five.
Rosberg, who called it a day after winning the championship, revealed that it was Hamilton's actions on social media during an official pre-race press conference ahead of the Japan event last season, which was pivotal in where the title was subsequently won and lost.
“It took a press conference that Lewis did to put him off a little bit,” Rosberg added.
“That gave me the win here last year.
“It unsettled his weekend a little bit and caused such a stir around him. He had a couple of mistakes, for example at the start, and that lost him the race.
“As a result I was able to pull away."
With just four races left of the 2017 season, Hamilton will aim to pull away from the chasing pack when the United States Grand Prix comes around in a fortnight, which will take place in Austin, Texas, on Sunday October 22.