The Finn hit the summit in the drivers' table after taking his first win of 2008 at the last round in Jordan, and enjoys a five-point lead over erstwhile title leader Sebastien Loeb, who could only finish 10th last time out after an accident on leg two.
"I'm first in the start order on Friday because I lead the championship," said Hirvonen. "It's not usually a big disadvantage in Sardinia and I'm not going to worry about that. My focus is finding the right speed because I can't afford to let any driver break clear."
He added: "At the end of the first day in Jordan, four cars were covered by less than 15 seconds. It could be just as close in Sardinia and I need to be in that group."