As good as Bartesaghi has been this season, most would still prefer to see Theo on the left hand side. Last season was a poor year, but he represents a lot of what Milan fans miss currently and that is proven quality.
Milan were incredibly strict with the wage bill for quite some time, especially since it even blocked some signings. In recent years, however, there has been a change on this front with more and more money invested in player contracts.
After the trial against Udinese, it seems difficult to imagine Massimiliano Allegri rushing back to use a back four. Ultimately, his side do not have the capability to withstand pressure as a back four, or even back two at times.
For Gabbia, that would be returning to the top of the table with Milan. Indeed, the Italian wants to win the Scudetto and as a leader of the squad, he will be enforcing similar demands on his teammates.