Pramac Ducati's Danilo Petrucci is having doubts about the superiority of the Desmosedci GP18 over last year's variant as it has underperformed in the last two races.
The bike, which was vastly superior at the Sepang test and at the season opener, came undone in Argentina and Austin when Petrucci and Lorenzo were both beaten by Jack Miller and Tito Rabat on the GP17.
"Maybe Jorge at that time was not so sure about his bike but for me in Sepang, Thailand and Qatar the GP18 was better. Now in the last two races for sure we have this doubt at the moment," said Petrucci, speaking at Jerez.
"After the first test in Sepang we said they are very similar. Maybe with the GP17 you have to ride for two or three laps to make a good lap time. During testing with the GP18 on the first or second lap you already found the right feeling. Then in Argentina we started to have some problems and we found the GP17 more competitive.
"Both Miller and Rabat were competitive in Argentina, maybe more than me and Dovizioso. For sure Jack did a great weekend in Argentina but even Tito was pushing Dovi until the last corner.
"For me Austin was a disaster race but we saw that with the GP18 we change a lot of things, we struggled to find the good set-up. With the GP17 they know the set-up and they know pretty well the bike, because it's the bike from last year with all the data.
"Like every year, with a new bike at the beginning of the season you need to improve, to develop. Hopefully things can change here but I don’t know sincerely. We'll see. I hope the bike makes a small step at this race."