Ducati's Andrea Iannone will hope to make a big step forward with the factory GP16 on Saturday after battling rear grip problems during free practice at Jerez.

Iannone finished 11th fastest and one place behind Ireland's Eugene Laverty, who impressed on the Aspar Ducati GP14.2.

The Italian rider, who finished on the rostrum in the previous round at the Circuit of the Americas in Austin, admitted day one had proved extremely challenging.

"It's a very difficult day for me because from the beginning this morning, everything is difficult, the feeling with the bike - not so bad on the corner, but when I pick up the bike it has a lot of spin and does not have a good acceleration," said Iannone.

"We tried to improve this situation and tried to change the setting on the bike but it is very difficult to control this situation at the moment. We will focus and check the data at 100 per-cent and try to improve.

"In Austin we used this [tyre] case and had some very good grip and good speed on the track. The feeling was good and here the feeling is good and not so bad on the angle, but once you pick up the bike it is very difficult to control the spin when I come back with the throttle," he added.

"But the engineers have some idea and I hope tomorrow we improve this problem."

Asked if the GP14.2 was better suited to the conditions at Jerez, Iannone was loath to delve too deeply into comparing the older evolution of the Desmosedici with his GP16.

"The GP14 has a very good grip and with the GP16 we lose a little bit of this and have less grip than GP14 on the rear, but we have more agility and the bike improves on the corner and braking points," he said.

"But now is another story, GP14 is GP14 and GP16 is completely different, the engine and character, it is a completely different bike."

Iannone lapped in 1m 41.017s, which left him 1.4 seconds down on the top lap set by Jorge Lorenzo.