Dani Pedrosa says he is still suffering from his collarbone injury after struggling for pace in practice at Valencia on Friday.
The Honda rider could only finish in eighth position in the previous race in Portugal, and wound up down in 12th place in today's practice, over a full second behind pace-setter Jorge Lorenzo.
Pedrosa admitted he was still struggling with his injuries and conceded the gap to the front was too big.
"The feeling is more or less the same as in Portugal except that this is a left-hand circuit which means there is a lot of braking into left corners - this makes it hard for me," said Pedrosa.
"I'm still not going really fast and because this is a short lap, 1.2s is quite a big gap to the front.
"Still, we have two more sessions of practice to go and I have the chance to improve my pace in those and move closer to the fastest times. We have to think about the race and improve things step by step tomorrow because there will be a lot of fans here supporting me and I really want to be ready for Sunday."
Andrea Dovizioso enjoyed a better day on his way to the fifth fastest time, the Italian claiming he was feeling optimistic on a track he has never shone before.
"I have always struggled on this track but today we have got off to a good start and I'm confident on the bike," he said. "We did some useful work today and the lap times from both the morning and afternoon sessions were reasonable, although they are not fast enough yet to be competitive in the race so we have more work to do.
"We tested some different set-up options and gained a clearer idea of the direction we will follow tomorrow. I'm fast in the first two sections of the lap, while I'm losing quite a lot in the last two sections.
"Our main area to improve is entering the corners and if we do this then it will give us a time advantage for the whole lap. I'm confident that we can move forward from our current position."