From eurosport.com :

Reigning MotoGP champion Valentino Rossi has admitted to being 'worried' by the pace of his Yamaha M1 after a disappointing test at Jerez last weekend. Constant vibration problems left The Doctor only tenth fastest on the final day, over a second off the pace, despite testing numerous Michelin tyres

Well, a bit of problems for the Doctor and his team in the beginning of the season could maybe make the season more interesting. Let a few others get a head start and watch Valentino catch up once they get the problems sorted out