(By Paul Virgo) Rome, April 5 - Valentino Rossi is pumped up for the new MotoGP season, which starts with Sunday's floodlit Qatar Grand Prix, saying he has found new motivation after returning to Yamaha. The nine-time world champion is back with the Japanese team after his 'dream marriage' with Italian outfit Ducati ended in divorce following two winless seasons. The 34-year-old, who won four of his seven premium-class world titles during his first stint at Yamaha between 2004 and 2009, never got to grips with Ducati's powerful but notoriously hard-to-handle race machines. But he was consistently among the frontrunners in the MotoGP pre-season tests after getting back in the saddle of a Yamaha. He came third in Thursday's first day of practice ahead of Sunday's night race in Qatar, although he led the way for much of the session and finished less than a tenth of a second behind the fastest time of his teammate, Spain's reigning world champion Jorge Lorenzo. "When I was at Ducati, expectations of me were high," Rossi told reporters at Qatar's Losail Circuit. "Everyone expected me to be in front, but I knew that it wasn't possible. "With Yamaha it's different. I grew up on this bike. I raced a (Yamaha) M1 for seven years and what's important is that the things I did automatically on it came back right away. "When I get on this bike and ride it I feel comfortable, even when I go slow. "That was never the case with the Ducati. Maybe some other riders can do better than me with the (Ducati) Desmosedici. "No matter. I'm used to winning and so this year I have totally different motivations". As well as Lorenzo, this year Rossi will also have to contend with Spanish Honda factory team rider Dani Pedrosa, who is many experts' favourite for the title. Some commentators think that Pedrosa's teammate and compatriot Marc Marques, who makes his MotoGP debut on Sunday after winning last year's Moto2 championship, may also be a challenger. Britain's Cal Crutchlow, who rides for the Yamaha satellite Tech 3 Team, is seen by some as the dark horse. Rossi said he was especially pleased at being so close to Lorenzo in the first official day of practice. "I performed even better than I expected," said Rossi, who is loved by fans for his outgoing, fun-loving character as well as his skill on two wheels. "I was as fast as Lorenzo. He's good and in the prime of his career, so if I manage to go as fast as hime, it means things are going well". Rossi is second in the all-time race-win standings with 105 victories and he will be looking this season to made inroads into the lead of his compatriot Giacomo Agostini, who won 122 grands prix in various classes in the 1960s and 70s. However, he has played down hopes that he might start the 2013 campaign with a win, saying he is aiming for a podium finish in Qatar.