The 44-year-old coach has urged his players to remain focused on domestic duties and not look ahead to their European date with the Primera Division champions
The Serie A champions face a difficult task to progress in Europe's most elite club competition against the Catalan giants, but Allegri's priority is the Giallorossi's visit to San Siro.
"We will play against Barca, but right now we have to think about Roma, who are very tough side to beat," the Italian coach told reporters at a press conference.
"After Saturday's game, we will have nine matches remaining, and keeping our four-point lead at the top will be important.
"That is why we have to think only about Roma and not Barca, just like it happened against Juventus in the Coppa Italia.
"Roma hold possession very well, and they have improved when they are not in possession."
The 44-year-old confirmed that Alberto Aquilani and Kevin-Prince Boateng are both available for the match, though he has not decided whether the Ghanaian will start the game or sit on the bench.
Robinho has been deemed unfit, while Thiago Silva's muscular problem should not prevent him from featuring against the Giallorossi.
Allegri went on to dismiss reports that club owner Silvio Berlusconi had blamed his training methods for the numerous injuries which have afflicted the squad this season.
"I spoke to him after the match against Parma, he only asked about those who were injured and if the players were tired.
"He tends to protect the players, he wants them to rest. But muscular problems are fewer than it may seem.
"We must still improve on this matter."