Andrea Dovizioso was struggling with the rear of his Ducati GP16 at Jerez as the Italian finished the first day of free practice in Spain in seventh place.
Dovizioso, who was the second top Ducati rider as Hector Barbera on the Avintia GP14.2 finished fifth quickest, posted his best time in 1m 40.737s as he trailed 1.1 seconds behind Yamaha's Jorge Lorenzo at the top.
“The start wasn't special but like the first two races you have to adapt to the tyres: we don't start from zero but every time it is almost like this because the tyres work in a different way in every condition,” said Dovizioso.
“It's the same for everybody and there is no excuse, so we have to work. The front works quite well and we are able to use the '34' when normally we are not good and our bike doesn't work so well, but here fortunately yes.
“The rear spins a lot and the grip is not so much, so it is very difficult to manage but it is the same for everybody,” he added.
“Anything can happen like in the first two races, we are not the fastest but we have to keep working like in Austin and we will see after the qualifying tomorrow, especially the pace with the used tyre.
“In this track the consumption of the rear tyre is so high, so what everybody is doing in the practice is not the reality in the race. Especially in this track, in these conditions, we have to use a lot of rear brake.”
Dovizioso's future is under question at Ducati along with team-mate Andrea Iannone after this week's confirmation that Jorge Lorenzo had signed a two-year deal with the Italian manufacturer for 2017 and 2018.