NASCAR Sprint Cup points leader Matt Kenseth will leave Roush Fenway Racing at the end of the season.
The 2003 champion will be replaced at Ford's leading team by last year's Nationwide Series title-winner Ricky Stenhouse Jr.
Kenseth's departure is a shock given his current status as the title favourite and as he is set to rack up his 500th Cup start as a Roush driver later this year.
However, since his car sponsor Crown Royal announced last year that it will leave the team, Roush has been unable to find a replacement backer for Kenseth's #17 Fusion.
"Of course, I'd like to thank Matt Kenseth for his many years of loyal service," said team owner Jack Roush. "Matt has been an integral part of this organisation for well over a decade, and we are extremely appreciative of his accomplishments and contributions to the team. We will always consider him a part of the Roush Fenway family.
"We're fortunate that we were able to tap into Matt's potential and bring him on board many years ago, and I'm proud that together we were able to combine the tools and the resources of Roush Fenway with his talent and determination to forge a partnership that yielded a championship at the Cup level and all of his 22 Cup victories, including two Daytona 500 wins."
"The #17 is positioned extremely well this season, and I'm committed to providing the team the best resources to continue their run for the 2012 championship. I have no doubt that Matt will do his part."
Kenseth has been linked to a move to Joe Gibbs Racing for 2013, with Joey Logano's contract up for renewal at the end of the year.
Although he did not comment on that speculation, he did write on his Twitter feed that his title push this year would not be affected by the news.
"I'm very thankful to Jack Roush for the opportunities he's given me over the past 14 years," Kenseth wrote. "Together we have enjoyed a lot of success and as a team we're as committed as ever to the remainder of the 2012 season and chasing a third Sprint Cup title for Jack and Roush Fenway Racing.
"Although I have nothing to announce regarding 2013, I think the timing of this announcement gives Roush Fenway Racing ample time to get things lined up."