MotoGP title runner-up Francesco Bagnaia couldn't hide his delight after trying the latest Ducati updates to a bike he already considers to be 'perfect'.

The Italian spend much of the final day at the Jerez test 0.8s clear of the field.

A late push by the likes of new world champion Fabio Quartararo (Yamaha), Alex Rins (Suzuki) and Pol Espargaro (Honda) slightly reduced chipped his advantage, but Bagnaia still finished the official 2021 track action half-a-second ahead of Quartararo.

"I'm happy," said Bagnaia, winner of four of the final six races this season. "Still we have more work to do, but I'm feeling great.

"I said that the old bike [GP21] was already perfect and we are improving on this perfect bike. So that is incredible.

"The lap time and the pace we are doing with medium tyres and with used tyres is incredible.

"This means Ducati have done a really great job because to improve a bike that was already fantastic is not easy.

"I'm not surprised because I know Ducati works a lot and every time we have a lot of things to try. And I'm so confident because one good thing is that I did a faster time than my qualifying with a medium tyre here and with the wind. So it's incredible. And we are working in a good direction for sure.

"For next year, we will have a lot more things to try in Sepang [February]."

That includes chassis updates, but among the new Ducati developments available at Jerez were a new fairing, exhaust and engine, as the Covid technical freeze comes to an end.

"The character of the engine is totally different and like always when something is completely new, you have to understand it and it's more-or-less at the same level as the old one but it's just the second day we are using it. So we still have margin," Bagnaia said.

"We need to work maybe more on the electronics, but in this moment the feeling was quite good."

The general consensus among the Factory and Pramac riders was that the new Ducati fairing provided perhaps the biggest step at this stage.

"We tried a different fairing that is good but still we have work to do on it because it totally changed compared to the old one and we are trying to understand if it can be better or not," Bagnaia said.

"I like it, because also it [looks] more nice, but it will be very important to choose one for next year.

"We need to do more laps with it, but at this moment I feel good with it and there are more good things than bad things. But it's not already decided."

There was also a long exhaust, which team-mate Jack Miller joked they called the 'didgeridoo'. But both riders were cagey on what changes it brought.

"For the exhaust, we were trying different things," Bagnaia said. "It's clear that Ducati is always is trying to understand very well the situation, the things and we tested this different thing.

"My feeling was more-or-less the same but for sure at home they are working and seeing the data and maybe something has changed.

"But [overall] at this moment the feeling with the new bike is good.

"We are just doing laps with the different things to understand which way to follow for next year. But already I feel great, so I have to say thanks to Ducati.

"I'm really confident, Ducati have all my trust for the development and I think me and Jack are telling great things to Ducati to help improve this bike."

The only specific area of weakness for the GP21, as highlighted by Ducati Corse general manager Gigi Dall’Igna, was entering fast corners at tracks such as Qatar and Assen.

"We are working on small things [to help turning] but this track is not the worst for the turning of the bike, so already at the start with the old bike the feeling was great," Bagnaia said.

"Also it was nice to see all the improvements we did during this season, because when I started yesterday, already in the first run I did an incredible lap time after 3 laps.

"It was very, very nice to see that our bike and also I have changed a lot during this season.

"I think this year is where I improved most in my life. Also I learned a lot of things and compared to the race here in May I feel better in the braking, the turning, the pace, also with used tyres.

"For sure it's something I worked a lot on, winning the races and being always constant has helped me a lot to be more competitive also with the used tyres.

"So we did a good step in front for sure this season, more than one step!"

Enea Bastianini was the next best Ducati rider in eighth, on the GP21, with Miller ninth.