Mercedes' Nico Rosberg Friday insisted he had nothing to fear from the arrival of Lewis Hamilton next season to replace Formula One veteran Michael Schumacher.
Rosberg, well ahead of seven-time world champion Schumacher, 43, in this year's standings, called Hamilton "very, very quick" but said he was confident of holding his own next year.
"My team-mate now is a seven-time world champion so the talent I'm up against is very high," said the German. "So I think it's going to be a similarly difficult challenge. I remember racing Lewis in go-karts so I know it's going to be tough.
"He's very, very quick, one of the best out there at the moment. It's great he's joining the team. I'm confident I will do well. I'm pushing hard to do well.
"How I compare with my team-mate remains to be seen. I'm not worried or anything, as such, no."
Hamilton, the 2008 champion, was second fastest behind Australian Mark Webber of Red Bull in Friday's second practice for the Japanese Grand Prix, with the retiring Schumacher and Rosberg 10th and 11th respectively.