Barrichello threatens to quit - In an interview, he said if he founds even a slightest indication of the team favoring Button, he will quit driving to that point.
Questions raised when Button won the Spanish GP due pit tactics - perhaps the biggest "alarm" was when the team pulled Barrichello to pits 2nd time - it was at least 5-6 laps before he should have come
He's determined that he won't accept position of 2nd driver anymore
Brawn tried to explain why Barrichello lost in the end to Button by badly working tires, but the driver didn't notice anything wrong with his tires