Casey Stoner has announced that he will leave Ducati at the end of this season, paving the way for his expected move to Honda.
The Australian joined Ducati from LCR Honda for his second year of MotoGP in 2007 - and stunned the paddock by winning his first race for the Italian squad at Losail and going on to take a dominant championship victory.
He has been unable to repeat that title success since, but has notched up 20 race wins and taken 19 poles with Ducati.
"I must thank Ducati for giving me such a great opportunity to race and win with them over these past four years," Stoner said. "They took a gamble when they signed me at the end of 2006 as I was unknown, but as we worked together we were able to win a championship, many races and challenge for the championship in the last two seasons.
"I have now decided to move on and I will have new challenges in the future, and different obstacles to overcome. But I will not forget these years with Ducati and the people I have had the privilege to work so closely with. So a big thanks to Ducati and all our sponsors who we have shared success with while achieving lifelong goals."
Stoner has been linked with a move to Honda since former Ducati boss Livio Suppo moved there late last year. He is expected to ride a third works bike alongside current Honda riders Dani Pedrosa and Andrea Dovizioso.
His departure from Ducati also leaves the way clear for Valentino Rossi to join the Italian team next year - with rumours of a team switch for the world champion having gathered pace in recent weeks.
Ducati team boss Filippo Preziosi paid tribute to Stoner's contribution to his outfit during the past four seasons.
"I would like to thank Casey on behalf of our fans and our sponsors, but most of all on behalf of all the people working at Ducati," said Preziosi. "The victories and emotions he gave us rewarded all the hard work and sacrifice we made.
"In these four years together we have had a lot of great moments. Securing the 2007 MotoGP world championship title and the victory at Mugello in 2009 were moments that we will never forget.
"In Casey we not only found an incredibly talented rider, but also an honest and loyal guy and that's why there will always be a strong and sincere bond between us, even as a competitor."