Competition

Earlier in his career Max Biaggi was considered Rossi's main rival. At one time his website did not even have Max's name; instead a glaring "XXX XXXXXX" was placed wherever his name should have appeared. Although they had not even raced against each other until 2000, the rivalry between the two had been growing since the mid-'90s. The rivalry died down as Rossi's consecutive World Championships and Biaggi's struggle to find support and a consistent rhythm with his races.
In his autobiography "What If I Had Never Tried It", Rossi makes a number of claims about the reasons for his rivalry with Biaggi, and some of the incidents which led to its escalation. The rivalry was also featured in the 2003 documentary film, Faster.
Rossi's closest rival in the 2003 and 2004 seasons was Sete Gibernau, riding with Team Gresini's Movistar Honda team on a satellite RC211V in 2004 and then on an all but in name factory RC211V, which Gibernau helped to develop, in 2005. Initially they were quite friendly in the paddock and off – Gibernau partied on occasions with Rossi at the Italian's Ibiza villa – but a souring in their relationship began in the 2004 season and culminated in the "Qatar Incident" that same season when Rossi's team was penalized for "cleaning" his grid position to aid in traction, along with Honda Pons' Max Biaggi, and both riders were subsequently forced to start from the back of the grid. A number of teams, including Gibernau's Team Gresini and the official Repsol Honda factory team, appealed successfully to race direction for Rossi to be sanctioned. Rossi and his chief mechanic, Jeremy Burgess, insisted that they were doing nothing more than what many others had done before when faced with a dirty track
Since then the two have not spoken and Rossi seemed to resolve to use the incident to apply psychological pressure on Gibernau. He is said to have sworn that after the Qatar race, which Gibernau won while Rossi crashed out after rising to 6th position, he would do everything to make sure that Gibernau never stood on the highest step of the podium again. Gibernau retired from Grand Prix racing after an unsuccessful, injury blighted 2006 season with Ducati and he never won another race after Qatar, prompting some in the Spanish and Italian motorcycle racing media to explain this fact by way of reference to the "Qatar curse." But he returned at the end of 2008, after tests on the 2008 Ducati convinced him that he could still be competitive in MotoGP, and signed to ride a Ducati in 2009.
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 in 2008. After numerous position changes, Rossi overtook Stoner down the corkscrew. The bold move caused Rossi to run wide into the gravel, 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, yet picked up the 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.
In 2008, Jorge Lorenzo joined Rossi in the factory Yamaha Motor Racing team, which started a new rivalry. After some great battles in 2008 and 2009 where Lorenzo went toe to toe with Rossi, 2010 saw Lorenzo dominate throughout the season to win the championship by amassing the highest points tally in history, scoring 383 points.