<P> In 2007, Casey Stoner emerged as a rival for Rossi . Coupled with a Ducati, the young Australian won the first race of the year, followed by many more victories resulting in his claiming of the 2007 MotoGP World Championship title . Stoner's and Rossi's rivalry came to a dramatic climax at Laguna Seca Raceway in 2008 . After numerous position changes, Rossi overtook Stoner at the Corkscrew . The bold move caused Rossi to run into the dirt and broken pavement on the inside of the right turn, and his rejoining the track came close to causing a collision between the two riders . A few laps later, Stoner went into the gravel on the slow entry into turn 11 . Stoner picked up his bike to finish second, while Rossi took the win . After this, Casey Stoner made the comment, "I have lost respect for one of the greatest riders in history ." For the comment, Stoner apologised to Rossi at the next race . </P> <P> In 2008, Jorge Lorenzo joined Rossi in the factory Yamaha Motor Racing team, which started a new rivalry . Rossi won the 2008 title, with Lorenzo suffering two serious crashes at Laguna Seca and China . In 2009, Rossi and Lorenzo resumed hostilities with Rossi emerging as champion again . In 2009, Rossi defeated Lorenzo in several tight battles, at Valencia, Assen, Sachsenring and, most memorably, Lorenzo's home race at Catalonia, after passing him in the final corner to take victory, in that part of the track where any overtaking was considered impossible . In 2010, Lorenzo finally emerged victorious in the championship battle, after Rossi first injured his shoulder in a motocross training accident, then breaking his shin - bone after a vicious crash in Mugello, missing four races . The most dramatic race of the season came at Motegi, beating Lorenzo for third place . </P> <P> Since his early racing days Valentino Rossi has had numerous nicknames . In the beginning he was known as "Rossifumi", inspired by Norifumi Abe, who made a spectacular debut in the 500cc class in Japan . </P> <P> Since dominating the 500 cc category later known as MotoGP, "The Doctor" has become the nickname of choice for Rossi . Two theories prevail as to why Rossi uses "The Doctor ." One is that Rossi adopted the nickname upon having earned a degree, which in Italy entitles one to use the title "Doctor ." Another, as spoken by Graziano himself, "The Doctor because, I don't think there is a particular reason, but it's beautiful, and is important, The Doctor . And in Italy, The Doctor is a name you give to someone for respect, it's very important, The Doctor...important ." Rossi often jokes, however, that the name arrived because in Italy, Rossi is a common surname for doctors . </P>

Who rode for yamaha when rossi ride for ducati