Ducati were 'already super-fast' but Aprilia, Honda and Suzuki have made 'a massive step'.

That was the verdict of Yamaha's reigning MotoGP world champion Fabio Quartararo at the end of the season-opening Sepang test.

The Frenchman finished the rain interrupted two-days in Malaysia with the seventh fastest lap time (+0.182s) behind three Ducatis, two Aprilias and a Suzuki.

Aprilia, the only manufacturer on the current grid without a MotoGP win, was perhaps the biggest surprise.

After riding for part of the Shakedown, Aleix Espargaro and Quartararo's former team-mate Maverick Vinales stayed top of the timesheets on day one of the Official test, then took second and fifth respectively on day two.

"They have two riders riding super-fast," Quartararo said of Aprilia. "It’s true they made more days [here] but the bike is working super well.

"If you check top speed, it’s super-fast. I was behind Aleix for half a lap and the turning was a lot. I’m impressed by them. For me Aprilia, Honda and Suzuki made a massive step."

Quartararo added: "Ducati were already super-fast at the end of the season. But the three that impressed me more are [Aprilia, Honda and Suzuki].

"To be honest I don’t think we [Yamaha] made a step like that, by far. But that doesn’t mean we aren’t competitive. It just means the others made a bigger step than us.

"We are struggling in some areas. It's strange to see I was struggling more with new tyres. Normally the time attack is one of my favourite things and I knew I could improve a lot more. I know the others made a big step in that area."

Quartararo was the only Yamaha rider inside the top 20 on the final timesheet but expects new team-mate Franco Morbidelli (24th) to be much closer at the coming Mandalika test.

"You always want someone that pushes you to the limit," Quartararo said. "Franco is going to be fast in the short future. In Mandalika he will be much closer.

"In the first part of last season when Maverick was there, I learned from him. The first race in Qatar, I saw what he did and I pushed to apply what I missed.

"Then Assen was the first time we both pushed ourselves to the limits. Assen for me was the most interesting qualifying. Even if I finished second because I made a mistake, I never pushed myself that much to the limit.

"So I think it’s helping [to have other fast Yamahas] but I don’t need someone to push me to go fast."