Kaka returned to Milan last week after four years away with Real Madrid.
"I think he will be in the starting XI," Allegri revealed. "He is in good shape, he has trained really well and he has the enthusiasm of a young boy.
"I think he is a little nervous about his debut tomorrow and it is only normal that he is missing a bit of match sharpness."
Kaka was widely considered as one of the world's best when he left San Siro, but Allegri thinks he still has plenty to offer.
"Kaka can give a lot to Milan. He has done some great things here at this club, he hasn't played a lot over the last three years in Madrid, but he has immediately put himself at my disposal.
"He spends a lot of the day at Milanello and he is a great example for the youngsters."
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