Valentino Rossi's ambition to end his Yamaha MotoGP career on a high suffered an early blow when he could only manage ninth in Friday practice for the Valencia season finale.
Rossi was fifth in the morning but ran into trouble during the afternoon, lacking grip and unable to find the right setting for his Fiat Yamaha.
The outgoing seven-time world champion, heading to Ducati for 2011, was only able to improve his time by a fraction in the afternoon, while team-mate and new world champion Jorge Lorenzo was fastest.
Rossi was 0.971sec behind Lorenzo.
"This morning was not so bad but the afternoon was not great," Rossi admitted.
"We weren't able to improve the setting from the morning and we had a few problems; we have some work to do because at the moment we don't have enough grip and the bike is difficult to ride.
"The times are quite close but we are in still ninth so we need to find a way to improve tomorrow.
"We will have a look at the data and see what we can come up with tomorrow because for sure we need to improve the grip if we are going to be competitive this weekend.
"It's a very important weekend, the last for me with Yamaha, so of course we want to try to be at the maximum," concluded the #46.
"This morning we tried some different geometries and settings and then in the afternoon we continued in just one way, but it's clear that we still have some work to do and we have some problems with grip," added team manager Davide Brivio, who will also leave Yamaha after Sunday's race.
"In the end we stopped a little bit early to consider the situation, and now we will look closely at the data to find the right way forward for tomorrow so that we can give Valentino a bike to allow him to ride how he wants here."