Rossi: Now I'm worried.

MotoGP World Champion Valentino Rossi says he's a worried man after finishing the final pre-season test in a lowly tenth position - and is crossing his fingers that Yamaha can cure their crippling chatter problems before the first race.

After having comfortably led the testing timesheets just one week earlier at Barcelona, Rossi - along with team-mate Colin Edwards - suddenly dropped down the timesheets at Jerez after vibration problems returned with a vengeance.

The root of the problem proved hard to pinpoint: Rossi initially felt that Michelin's latest tyres were the main cause of the chatter - and was confident of finding a cure at Jerez, saying that he would only worry if the chatter was still present on the eve of the season-opening Spanish Grand Prix (to held at the same circuit, on March 26).

However, as he left Jerez on Sunday, Rossi claimed to be "quite worried" after the combined efforts of the French tyre manufacturer and Yamaha failed to solve the vibration issue during three days at the racetrack.

Camel Yamaha completed the test with Edwards in seventh - 1.3secs from fastest man Loris Capirossi - and Rossi tenth, almost 1.5secs from the top.

"Yesterday I was confident that we could find some big improvements today but honestly that hasn't happened and now I am quite worried," revealed Rossi after day three. "The vibration has remained and at the moment we don't know how to solve it.

"Yamaha and Michelin have done a lot of good work today and we've tried many different tyres and settings, but we are still slow. This is the last test and throughout the whole pre-season period we've always been fast and the bike has felt good, but this test has been completely different.

"At the moment I am not sure what will happen in the race, we'll have to wait and see. I hope that Jeremy (Burgess - crew chief), together with the Japanese engineers and the Michelin technicians, can use all the data they have now to understand the problem and see how to solve it," concluded the seven times world champion.

Team-mate Edwards confirmed the seriousness of the problem - saying that it meant they are without a "winning pace" for the first grand prix - but, like Rossi, is pinning his hopes on a solution away from the racetrack.

"It would be nice if I could say that we've solved all our problems today, but sadly it's just not the case and we're still struggling a bit," began the Texan. "I think we've really gone in circles a bit here. We've changed a lot of things and we haven't really concentrated on a race simulation or the endurance of the tyre, we've just been trying to find ways to dial out the problems we have.

"To be honest our pace isn't bad but it's certainly not a winning pace, which is frustrating when we saw in Barcelona last weekend how great our package is when it's all working! Yamaha and Michelin have more than enough information after three days and I am confident that they will come back with something to solve our problems. Anyway, that's it for testing!

"I'm heading home for ten days to chill out a little bit and let's hope that the new stuff we have when we come back for the race will help us out so we can challenge for a win," Colin concluded.

"After this test we don't know how the race will go, but it's been very important to have this chance to test before it," stated team director Davide Brivio. "As the riders say, we've tried many different things and collected a lot of information. Now our engineers will have ten days to work on this and come up with some new ideas and solutions.

"This is the end of winter testing and we've seen that our bike can work very well at different tracks. We need to understand why this hasn't been the case here, but we're convinced we can find a way forward and we know that we still have a very good package," he added.

Free practice for the season-opening Spanish Grand Prix will take place at Jerez on Friday March 24.