Brazilian Felipe Massa announced on Tuesday he was leaving Ferrari at the end of the season.
"From 2014 I will no longer be driving for Ferrari," the driver said in a post on Instagram and Twitter. "I would like to thank the team for all the victories and incredible moments experienced together.
"For next year, I want to find a team that can give me a competitive car to win many more races and challenge for the Championship...," he added.
While speculation about Massa's future has been a regular occurrence of recent seasons, this time the Brazilian recognised he had run out of road and his exit could leave his country without any driver on the starting grid.
Massa has not won since 2008, when he was overall runner-up, and has been on the podium just once this year. But he was a loyal team mate to Alonso who made clear who he would rather have in the other red car.
"I have a lot of respect for Felipe. We've been working very hard and close for four years to give Ferrari the maximum," Alonso said in a response to fans on Twitter on Monday.
"Whatever decision the team will take will be good for me and we will keep working to give Ferrari the best results possible."