Allegri will return to San Siro for the first time in a competitive match since he was fired by AC Milan in January.
Neither team has dropped points this season, and Juventus hasn't conceded a goal in a competitive match since April.
The only other side to have won both its opening matches is Roma, which hosts Cagliari on Sunday.
Here are some things to know about this weekend's matches in the Italian league:
Massimiliano Allegri spent 3½ seasons at Milan and led the Rossoneri to the Serie A title in his first year in charge in 2010-11.
However, he struggled after Milan sold its best players, with several others retiring.
The 47-year-old Allegri was a surprise choice to replace Antonio Conte when the Juventus coach resigned in the offseason, shortly after leading the squad to its third straight Serie A title.
However, Juventus has won both his opening league matches as well as beating Malmo 2-0 in the Champions League on Tuesday.
"It was important to beat Malmo," Allegri said. "Now we can focus on the match at San Siro. Milan have started very strongly and have bought really well.
"I have a great relationship with (Milan vice president Adriano) Galliani, he called me before the Malmo game to wish me good luck. But it's obvious that now we'll be enemies on the field."
Allegri returned to San Siro with Juventus in August for a traditional preseason tournament, losing 1-0 to Milan.
AC Milan has also started strongly under coach Filippo Inzaghi, playing entertaining football and opening the season with victories against Lazio and Parma.
The Rossoneri hadn't won their two opening matches in eight years — when they also played Lazio and Parma.
"It's been a long while since we had such a positive atmosphere at Milanello and in the club," Milan vice president Barbara Berlusconi said. "There is a desire to do well, enthusiasm and togetherness. Also my father, Silvio Berlusconi, has come back to take care of Milan with renewed passion and commitment. This is good news."
Both teams are beset with injuries to key players ahead of Juventus' trip to AC Milan.
However, it is Juventus which is faring the better as it prepares to welcome back midfielder Arturo Vidal and defender Andrea Barzagli. Andrea Pirlo is also nearing a return but is unlikely to be fit in time for a return to his former club.
Milan will definitely be without goalkeeper Diego Lopez, who injured himself trying to reach a goalbound backpass in Sunday's 5-4 victory at Parma. Defender Alex and midfielder Riccardo Saponara were also ruled out this week.
Torres is likely to be on the bench as he prepares for his Milan debut.
Roma is the only other squad in Serie A to have won both its opening games. It also got its Champions League campaign off to a strong start with a 5-1 victory over CSKA Moscow on Wednesday.
On Sunday, the team hosts Cagliari.
"Apart from the huge scoreline by which we beat CSKA, I think it was very important above all to start the group with a win," Roma captain Francesco Totti said. "As I often say, now we have to be good in immediately preparing mentally for our next match. We're playing Cagliari on Sunday and we must not think of anything else."
Juan Manuel Iturbe is unlikely to be fit after getting injured following a strong opening 25 minutes against CSKA, which saw him score once and set up two other goals.
Gervinho — who scored two goals and had an assist — will likely be partnered by Alessandro Florenzi.
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