The veteran keeper admits his side will need to be fully focused as they look to move clear at the top of Group B in the race to reach the World Cup
Cesare Prandelli's men can take a huge step towards automatic qualification from Group B for Brazil 2014 with a win at Stadio Renzo Barbera in Palermo.
Buffon and his side sit four points clear of Bulgaria with four matches to play but the 35-year-old Juventus goalkeeper is concerned about his team's chances against Lyuboslav Penev's men.
"I'm quite worried for the match against Bulgaria, as always before matches that become decisive for qualification," Buffon said on Wednesday.
"We deserve the qualification for what we've done up to now but we haven't gained it yet. We will have to prepare and face the match with great attention to take another important step forward."
In PSV's Stanislav Manolev and Aston Villa signing Aleksandar Tonev, Bulgaria have two of the group's top scorers with three goals each.
Buffon is wary of the individuals in Bulgaria's side and warned his team-mates the visitors would try and punish them on the counter-attack.
"Bulgaria are a team with two or three important single players but they're also a very close group that knows very well how to face these kinds of games, trying to defend well and counter-attack," said the veteran goalkeeper, who is in line to equal the record number of performances for the Azzurri in the upcoming qualifiers.
"They have three or four good runners and they're in good condition. We need to be good at limiting them."
Buffon was also full of praise for Prandelli, who may step down after the 2014 tournament according to reports in Italy.
"Prandelli's touch was and is very important because he made us believe that we can try and reach aims and win also having fun, playing well and improving the technical aspects of a game," Buffon added.