Marlboro Ducati's Nicky Hayden has said he doesn't know why he wasn't able to replicate his laptimes from the Catalan MotoGP free practice during testing yesterday despite conditions being similar.

The former world champion wasn't able to get under the 1'44s mark even though in the cooler temperatures that replicated Saturday's free practice session, he set a 1'43.6

“It wasn’t the day I had hoped for, seeing the progress we had made over the weekend. In Saturday morning’s practice, when it was a little cooler and the conditions were similar to those of today, I lapped in 1m43.6 while here I haven’t gone under 1m44 and right from the start I didn’t have the same feeling as I had over the weekend," said the American

I don’t know why, also because we worked so hard, but I hope that the data collected is of use to the engineers so we can prepare well for Assen."