Nicky Hayden was puzzled by a lack of acceleration from his Ducati after finishing Laguna Seca practice in a lowly 14th place.
The America had hoped that he would be able to capitalise on recent progress and get a strong result at his home track, where he has won twice in the past, but instead remained in the midfield today, to his confusion.
"We're near the back again so that's not cool and not what I was hoping for," said Hayden. "In some places the bike feels quite good but in other places, coming out of the corners, it feels pretty flat and I don't have enough acceleration.
"Usually this is a strong point of the Ducati so it's a little strange so we'll have a look at the mapping and see if we can figure out the problem tonight. Normally around here you have a lot of wheelies and I don't have any so it's obviously something we need to put right."
Hayden has yet to qualify higher than 12th since joining Ducati, but has started to show better form in practice and over race distances in recent weeks. He arrives at Laguna fresh from a season-best result of eighth place at Assen, which could have been sixth had a handlebar not worked loose.