A win is a must for Juventus. They can easily climb up as long as they take three points from Milan soon. They shall focus on how to beat their next opponent, and may be struggle to do that.
Juventus's gap to the Napoli is very thin. They can climb to the first position when their opponents will miss three points soon.
I haven't seen a rumor about Juventus's January transfer to buy a new player, but they will sell Fagioli for 25m.
The teams are very close, but in order to move up, Juventus needs all the other teams to lose points, which is unlikely to happen. And Milan with Fonseca is also gradually improving, they don’t always manage to play well, but some games, like the match with Real, they do very well, so I wouldn’t rush to say that Juventus can beat Milan. Inter will beat Verona, Napoli will probably beat Roma too, so Juve won’t be able to reach these teams.