Valentino Rossi says Yamaha is in ‘trouble’ after a difficult opening day of practice at Motegi for the Japanese MotoGP, in which all three factory riders finished outside of the top 10.

The 2017 YZRM1 has struggled with a lack of traction in extremely hot conditions and in the wet this season, and while a prototype 2018 chassis introduced at Silverstone has aided with the former problem, its wet woes persist.

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Maverick Vinales ended the first session ninth, but was 1.5 seconds off the pace, while Rossi and factory wildcard Katsuyki Nakasuga languished down in 19th and 23rd respectively.

Vinales and Rossi finished second practice 11th and 12th in the standings, but were still missing 1.5s to session leader Andrea Dovizioso.

Rossi – who is still recovering from a broken right leg sustained at the end of August – said the team tried numerous alterations to the bike on Friday, but was still at a loss as to why his issue could not be resolved.

“Sincerely, we tried to do a lot of things with the bike, but we are in trouble,” Rossi said to

“And we don’t understand why, because last year I was very competitive in the wet.

“I had a good feeling with the old bike, but this year we are struggling. It’s something strange.

“We try to modify, but at the end we are quite far from the top and the bike is difficult to ride, and in general the problem is a bit like in the dry; we don’t have rear grip.

“When we race with this (2018 prototype) chassis in the dry, like at Silverstone and Aragon, it is not so bad.

“We have some problem, but we were quite competitive. But in the wet, no way. Very difficult.”

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Rossi admits to being left frustrated by the pace of the Tech3 riders – Johann Zarco was fifth after second practice – on the 2016 bike, and is concerned the team has already found its peak performance level for this weekend.

“If you look at the data with the old bike, it is a big frustration because, f***, in the corners, no way. So we need to try to understand, especially for next year.

“We are quite worried because today we do a lot of modifications, but at the end, no way.

“So we don’t have a lot more to do than this, this weekend, so we need to understand for next year.”

“Already in corner entry I’m very slow. I don’t feel the rear. In general, there is always (a lack of rear grip) and in acceleration we have a lot of spin.”