Barrichello is thrilled to be racing in front of his Brazilian fans for the first time since joining IndyCar, but admits he still is adapting to the series and won't be racing among the leaders on Sunday.
The Formula One veteran said that despite racing at home, he will be facing the same difficulty he encountered in his first three races of the season, when his best finish was an eighth place in Alabama.
He said his unfamiliarity with the challenging circuit on the streets of South America's biggest city will leave him at a disadvantage over most of the field.
"My biggest problem is not knowing the tracks, that has given me the most difficulties so far," Barrichello said. "That's going to be the case again here in Brazil. The only advantage I'll have here is mental, the advantage of being at home, of wanting to perform well to the fans. But the difficulties will be the same as before."
Barrichello tested well before the season, but was not able to finish near the front in his first three races. He opened his season with a 17th-place finish at St. Petersburg after a mechanical problem, then was eighth in Alabama and ninth in Long Beach after starting 22nd.
"I'm still not 100 percent comfortable with the car, I need more time, it's completely different from what I used to drive in Formula One," he said. "I'm being able to show some improvement during the races because I'm learning the tracks as the race progresses."
The 39-year-old Barrichello said he expects even more difficulties in Sao Paulo because the track will only open to drivers on Saturday. Drivers usually can start racing Friday on non-street circuits.