Nico Rosberg is refusing to comment on speculation that his team mate Lewis Hamilton threatened to quit Mercedes earlier this year.
Hamilton reportedly handed his notice in after he collided with Rosberg in May's Spanish Grand Prix.
He then was said to have refused to participate in the Pirelli tyre test earlier this week. While he eventually did take part in the test, he left the circuit after only a handful of laps after it was said he was feeling "unwell".
"I read about the (Abu Dhabi) test," Rosberg told the Kolner Express newspaper.
"But I do not know what he is doing now or what he's been doing. The whole season he was as focused as never before.
"The fact that I took the title from him is a great satisfaction, because it was Lewis," said Rosberg. "For me, he is one of the best ever."
Rosberg also insisted that the pair's frosty relationship actually works well for the good of the team because of their mutual respect.
"I think he has always respected me," he said.
"We were friends since we were 13 years old, which helps for when we are racing against each other. I see that continuing," he added.