Pogba faces his former Juve teammates in the Champions League on Tuesday night.
“It's an important game because if we win we can start thinking about going through," Allegri said in his pre-match Press conference.
“They're a strong team, very physical, and we'll have to play well technically.
“Pogba side we'll find a squad of strong players. Tomorrow is also a match between a lot of good young players: they have [Anthony] Martial, [Paul] Pogba, [Marcus] Rashford; we have [Paulo] Dybala, [Federico] Bernardeschi, [Joao] Cancelo, [Rodrigo] Bentancur.
“These are young players who must be the future of world football. Tomorrow is an important test for us, and also for those individuals. Playing in this stadium against a great team is a good test.
“They have technique, speed ahead and physicality. They are a strong team, built to win.
“They also have an experienced Coach [Jose Mourinho] and we need to play well tomorrow.
“We also need to manage games better, on Saturday [against Genoa] we stopped too early and tomorrow we need to be in the game for 100 minutes, because these games are never over.
“You just need to look at what happened against Chelsea when they [United] conceded goals on high balls, an area in which they're very strong.
“We need to play football, because physically we could suffer."