sentences:  Troy Bayliss attempted to defend his title, riding once again a Ducati 999.Though 999 production ended in 2006 and the bike was replaced by the Ducati 1098, Ducati produced 150 limited-edition 999s at an elevated race specification to satisfy homologation requirements.Bayliss' main rivals in his title defense included former MotoGP rider Max Biaggi riding a Suzuki, 2004 champion James Toseland riding a Honda and Noriyuki Haga riding a Yamaha.