Dani Pedrosa, a five time grand prix winner at Valencia, made a steady start to the 2010 MotoGP event as he continues to get up to full pace after his collarbone injury and subsequent operation last month.
The Repsol Honda rider was only twelfth fastest in both sessions, and is struggling with the many left hand turns.
“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," he said. "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.”
Pedrosa holds a 19 point lead over Valentino Rossi for second in the final world championship standings.
Pedrosa's team-mate Andrea Dovizioso was third in the morning, then fifth in the afternoon.
“I have always struggled on this track but today we have got off to a good start and I'm confident on the bike," said the Italian. "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.”
Dovizioso is ten points behind fourth in the championship Casey Stoner, who was second fastest for Ducati.