BMW Sauber's Jacques Villeneuve, who crashed in last weekend's German Grand Prix, will miss this weekend's Formula One race in Hungary.
Kubica joined BMW Sauber as a test driver at the start of the season
The Canadian will be replaced by test driver Robert Kubica, who will be the first Pole to compete in an F1 GP.
"Jacques has informed us that he is not ready to race after his Hockenheim accident," BMW Motorsport Director Mario Theissen said in a statement.
"Robert has made an outstanding impression with the team so far."
Theissen added: "We have not made a decision on who will drive the car either in the remaining races of the season or next year."
I'm determined not to let BMW Sauber down
Ex-world champion Villeneuve crashed twice at Hockenheim, effectively eliminating team-mate Nick Heidfeld on the first lap before hitting the wall mid-race.
No medical reason has been offered for Villeneuve's absence, which is bound to fuel speculation over his future with the team.
The 21-year-old Kubica said his opportunity had come ahead of schedule but stressed his determination to seize his chance.
"I had prepared myself for a whole year without actually competing in any races, so I'm even happier to get this opportunity," said the former Renault World Series champion.
"And I'm proud that the BMW Sauber F1 Team has such confidence in me. I'm determined not to let them down."