Although still under contract to Caterham, the team's new management has sidelined the popular Japanese for at least the Belgian grand prix in favour of 32-year-old F1 rookie and reigning Le Mans winner Andre Lotterer.
"It's a shame not to drive Spa," Kobayashi told his more than 150,000 Twitter followers. "I feel sorry for all my supporters but this is motor sports -- I hope not!"
Able to bring little to the table for the increasingly sponsorship-minded new Caterham chiefs, Kobayashi has earlier lamented the increasing power of the 'pay driver' but also life at the back of the grid in 2014.
Asked in Hungary recently if the uncompetitive Caterham is giving him the tools to showcase his famously attacking style, he admitted: "Not really!
"It's not really happy but I need to hope that one day I'm going to make something, a really exciting race. A 'train' race is not really exciting," he said.
Now, after his ousting, Kobayashi posted a Leonardo da Vinci quote to his Twitter followers in Japanese.
In English, the quote is: "Every now and then go away, have a little relaxation, for when you come back to your work your judgment will be surer.
"Go some distance away because then the work appears smaller and more of it can be taken in at a glance and a lack of harmony and proportion is more readily seen," the fabled Italian painter had said.
Caterham's decision to axe Kobayashi has been criticised by former team technical boss Mike Gascoyne, who is still involved in the wider Tony Fernandes-led Caterham Group.
"Such a shame that Kamui is not driving for Caterham at Spa," the Briton said on Twitter. "He was their only hope of regaining tenth place but (the decision is) typical of the new management."