Nico Rosberg says Lewis Hamilton got his engine settings wrong in the second free practice session at Interlagos on Friday and remains wary of the newly crowned drivers' champion ahead of qualifying for the Brazilian Grand Prix.
Rosberg saw his Mercedes team-mate and fierce rival Hamilton capture a third career Formula One drivers' crown at the United States Grand Prix in Austin, Texas, last month.
The German will this weekend be racing to secure second in the drivers' standings ahead of Ferrari's Sebastian Vettel.
But the pleasure of denying Hamilton a first victory at Interlagos, the home race of late Brazilian great Ayrton Senna, an idol of the Englishman, may be a greater incentive.
Rosberg made promising strides in the direction of a successful penultimate race of the season by topping the time charts at the end of FP2 following a lap of one minute and 12.385 seconds, 0.458s quicker than Hamilton.
It remains to be seen if the pace shown by Rosberg will translate to a place on the front of the grid, with the 30-year-old claiming his colleague got it wrong after initially going fastest in FP1.
"The gap to Lewis is definitely not the real picture because he got his engine settings wrong and there's [a] big lap-time [difference] in that," Rosberg said.
"But still it's a decent start and I'm pleased with the direction I've got."
Hamilton's preparations have been less than ideal as he seeks to end his wait for an Interlagos victory. The former McLaren man crashed one of his own cars in Monaco earlier this week, an incident he attributed to "tiredness after partying" to celebrate his title triumph.
And those exertions could still be taking their toll, with Hamilton confirming Rosberg's theory about a failure to adapt to conditions following heavy rain between the two sessions.
"I didn't change anything in the car for the second free practice, so I didn't follow the evolution of the track," he said.
"Maybe that's a disadvantage. I'll make some changes tonight I'm sure.
"These set-up changes take a long time and I was kind of stuck with a choice that I'd made in FP1 that probably wasn't the right one."
Qualifying will take place on Saturday with the race due to be held a day later. Rosberg won last year, ahead of Hamilton, and a repeat of that outcome on Sunday is sure to satisfy the German.