Seems like every few weeks some comes charging into the comments proclaiming Milan can play the 4-2-3-1!! Truth be told it is like an epidemic. Not sure how or when the 4-2-3-1 became the end all and be all for tactical formations. For a while the en vogue thing to do was shoe horn players into the 4-3-3. Everyone was doing it, and like the proverbial bridge, if everyone jumps why can't we. I waxed lyrical on Turkey day on why the 4-2-3-1 would not work yet we are still discussing to this day! So many versions of this formation kicked around...
Kaka- Honda Ses
All with the same two fatal flaws, the wrong players in the dual pivot and the lack of true wingers will expose this formation time and time again, yet somehow we continue to stubbornly state:
Only a 4-2-3-1 formation could truly squeeze out the abundance of talent that Allegri has up front.
What this self professed "genuis" above fails to mention is that while it squeezes attacking talent, it murders the defense and Milan's already horrid goal differential will only get worse.
Alas, I have ranted long enough, I wanted to actually say something constructive in this post and it related to derivative formations. During my Coach classes you learn about formations and how they can be morphed into something else because a few things remain, ie the spine and the core. Both of these "things" are often found right smack dab in the middle of any formation. The 4-2-3-1 at it's core and spine relies on two things the dual pivot and the Center Forward. The dual pivot is a CM combination that can be found in other formations as well, or derivatives, such as the 4-4-2 (4-4-1-1) and the 4-2-1-3, simply put you can take a 4-2-3-1 and move wingers back and forth to create a new formation from your base. The reason for this is the player traits in the core roles remain the same.
Apart from not having wingers, in my opinion, Milan lacks the players to work the dual pivot, which in turns makes this set of formations above and how they are worked a failure. Many seem to think Monty and DeJong can work a dual pivot, but this is far from the truth. Montolivo lacks the characteristics for this role, ie ability to press and tackle, and a different sort of midfielder to pair with NDJ to make this work. Instead Monty is more suited for a three man midfield, which is what Milan's core foundation is and has been under Allegri. With a three man midfield at the core, derivatives can be 4-3-2-1, 3-5-2, or a more classic 4-3-3, as Milan has deployed in the past to a bit more success. Point being, you can move within the derivatives formations and find some success, but you can't uproot the whole thing hoping for the best.
At the end of the day Milan's lack of wingers is the first and foremost problem with the 4-2-3-1 but mix in the lack of a real dual pivot and the change in core formation, it is a recipe for disaster.