Williams has announced Bruno Senna as Pastor Maldonado’s race teammate for the 2012 season.
"That’s right, I will not be driving the Williams this year," veteran Rubens Barrichello, who had hoped to contest a 20th consecutive season, told his masses of Twitter followers in Portuguese.
"I wish my friend Bruno the best of luck. For me, the future is wide open."
Senna, whose great uncle Ayrton died at the wheel of a Renault-powered Williams in 1994, will make his track debut with the famous British team at Jerez on 9 February.
It is believed the 28-year-old is bringing millions in sponsorship to the team.
"I want to get some good results in return for the support my country has given me to help get me to this position today," he said.
"Knowing people have chosen me to bear their name gives me even more motivation to create good memories for them."