Je viens de trouver un article sur motomatters,excellent site je le repete,c'est bien ce que je pensait il a ralenti a cause d'un pilote qui le suivait en l'occurrence Barbera,son pneu n'etait pas en temperature :
The sequence of events is fairly well known: After two fast runs early in the second session of free practice, held during the morning, Valentino Rossi went out for a third time. He had just fitted a brand new tire, the harder of the two compounds Bridgestone brought to Mugello. He went out for his out lap, and crossed the line to start his first full lap.
In the first two sectors, Rossi was as fast as on other laps. As he ran through Arrabbiata 1, he found Hector Barbera following him, and so he slowed right down, to prevent Barbera from following. According to one team manager who witnessed the entire incident from trackside, Rossi was slow for almost a kilometer, creating enough space ahead of him to get back on the gas. He was just under 9 seconds slower through the entire third sector than normal, taking 44.5 seconds, instead of between 35.7 and 36.2, which is normal for a fast lap.
As Rossi entered Correntaio, the downhill long hairpin, the Fiat Yamaha rider got back hard on the gas. He was pushing very hard out of Correntaio and entered the left-right flick of Biondetti 1 and Biondetti 2 at full speed. After Rossi flicked the bike left and got on the gas, the rear wheel of his YZR-M1 started coming round on him, before catching and flicking him off high into the air. Rossi landed very badly, breaking his tibia and ending his weekend, and any hope of racing for the foreseeable future.
http://www.motomatters.com/news/2010...o_rossi_e.html