Nico Rosberg believes Mercedes is closing the gap on rival McLaren, despite the team's failure to score a point in the Korean Grand Prix.
Rosberg retired from the race on the opening lap while team-mate Michael Schumacher struggled with his car's handling to finish in a distant 13th position.
Although Rosberg conceded it was hard to predict what he could have achieved in the race judging by Schumacher's problems, the German reckons the gap to McLaren is being reduced thanks to the updates introduced in recent races.
"The car was okay. We made a little bit of progress there [Japan], and we had some new bits here. Especially compared to McLaren I think we are getting a little bit closer, so there are some positives there," Rosberg said in his post-race video blog.
"In the race I don't know what I could have done, but for sure Michael was struggling a lot, so that didn't look very good. It definitely looked like we moved forward there, we need to look at why.
"Maybe because the temperatures dropped because it was the afternoon here and the tyres get clod and there's graining in the front. The tyres change so quickly, it's a big issue."
Rosberg, who was forced into retirement after Sauber's Kamui Kobayashi crashed into him at the start, failed to complete a single lap for the second race in succession.
In Japan, the Mercedes driver was involved in the accident caused by Romain Grosjean at the start.
Rosberg believes some of his rivals need to "calm down".
"Two weeks, including Japan, that it has been really poor. Terrible to go out in the first lap both times. There are just a bunch of drivers who are pushing too much, taking too many risks. They need to calm down a bit, I think."