Cesare Prandelli will be without the AC Milan star as well as Riccardo Montolivo for the meeting on Friday, while Gianluigi Buffon could equal the Azzurri's appearance record
Cesare Prandelli's are four points clear of this week's second-placed opponents in Group B, with the pair unbeaten so far in their campaign.
Wins against Bulgaria on Friday and the Czech Republic on Tuesday would put the Azzurri on the brink of a place in Brazil where they can make amends for their poor showing in South Africa three years ago where they failed to win a match and were eliminated at the group stage.
Prandelli, who will be without key trio Mario Balotelli, Pablo Daniel Osvaldo and Riccardo Montolivo due to suspension, is concerned Bulgaria could be in better shape than his side since the domestic season in the eastern European nation began several weeks ago.
"I am worried, above all, about the physical conditions," he said on Monday.
"Bulgaria is in good shape, they can give us some problems. We have to contrast Bulgaria with lots of quality in the middle of the field and with lots of running along the touchlines.
"Bulgaria are in good physical condition, it will be a difficult match and historically we have always had problems in September. The message is thinking about winning these two matches before talking about the World Cup."
Italy stalwart Gianluigi Buffon could equal the all-time appearance record of 136 caps for his country against Bulgaria at the Stadio Renzo Barbera.
The Juventus keeper was part of the side that won the World Cup on penalties in 2006 and he believes representing his country means as much now as it did when he made his debut back in 1997.
"There is a sense of honour when you represent your country," he explained.
"You understand that with time, with maturity. Every appearance with the national side is not just a game, but something more.
"I personally would not turn down a call-up. It would be like spitting in the face of good fortune, something that so many people want but only a few have the chance to experience."
In contrast, Bulgaria boss Lyuboslav Penev has called up uncapped goalkeeper Georgi Kitanov into his 21-man squad.
Penev has seen his side's campaign falter somewhat in recent matches, drawing four of their six qualifiers, though he will take heart from the 6-0 win over Malta in March as well as the 2-2 draw with Italy in the reverse fixture.
His side also remain in pole position to secure a play-off place, sitting a point ahead of the Czech Republic in third in Group B.