Nicky Hayden concedes that Ducati are on the back foot in Austin after missing out on last month's private test at the Circuit of the Americas in Texas.
Hayden was ninth fastest on his Desmosedici during free practice on Friday.
The American's best lap 2m07.699s left him 2.668s off the pace of Marc Marquez at the top and 0.443s behind Alvaro Bautista in eighth position on the Gresini Honda.
Hayden, who had previously lapped the new circuit on a road bike, enjoyed the experience of riding a full-blown MotoGP machine at the track for the first time on Friday as he got down to the serious business of closing the gap to the top.
“It was great to get out and try the track on a MotoGP bike, as it's really a first-class circuit and facility,” said Hayden.
“This morning the biggest challenge was the lack of grip; on a new track with not much temperature, the tyres were simply too hard, though the conditions were better in the afternoon.
“We had a few problems with the rear, and when we made that better, that put too much load on the front,” he added.
“We knew it was going to be tough, since the other manufacturers tested here and have a lot of data.
“We've got some catching up to do, but I certainly hope to get closer tomorrow.”