I used this 4-2-3-1 tactic in the first season of my Man United save. It's a very versatile tactic because it has simple instructions. In possession the focus is on creating chances though passing into space, which makes use of any space left by the opposition which it can take advantage of, therefore facilitating chance creation. It employs a high tempo but shorter passing which is used to reduce the chance of unnecessarily through more direct, harder to complete passes, yet making sure to move the ball up the pitch quickly. In transition it looks to counter-attack, which you'd definitely need faster players for. Out of possession the aim is to keep the opposition high up the pitch by using a high press and high defensive line, which although can be vulnerable to balls in behind, which is used to tighten the shape. It doesn't allow the opposition much unchallenged time on the ball with the much higher pressing intensity, aiming to suffocate their play. Get stuck in is used to make sure that the players tackle like they mean it, with full intent on winning the ball back.
The tactic uses playing out from the back with an effective build up where the IFB creates a back 3 with the two centre backs, the back 3 also protects against counter attacks well which makes it safe to counter-press without having to worry about being caught out on the break. The segundo volante is a very versatile role in the tactic as when in possession rotates between attacking and defensive midfield to either create a 3-2 build up shape or to create the shape you'd see in the midfield of a 4-3-3 DM. The other holding midfielder is a BWM who's the more defensive-minded player in the double pivot as his aim, as implied by the name, is to win the ball back which protects the defensive line from the opposition advancing. The WB is used to provide a wider option for build-up and is also used to create overloads on the right side of the opposition's defence with the IW by making forward runs down the left meanwhile the IW, on the same side, aims to run at the opposition and make threatening runs in behind to give the defence something else to worry about. The right-sided IW, who's job is to cut across the defence when he's in possession, is actually told to stay wider which can help with providing the wide option on the right as the IFB stays back and sits narrow. The AP sits in the pocket between the their defence and midfield and aims to spread the ball around and create chances. He is told to roam from position which means he can influence more of the play around different areas of the pitch. The final role is the lone AF who plays very high against the defensive line; this helps with giving the centre-backs more to think about as he is always threatening in behind: they can either prevent his runs by dropping deeper, therefore creating more space to attack in front of the defence, or they'll leave space in behind for him to make runs and score goals.
The tactic uses playing out from the back with an effective build up where the IFB creates a back 3 with the two centre backs, the back 3 also protects against counter attacks well which makes it safe to counter-press without having to worry about being caught out on the break. The segundo volante is a very versatile role in the tactic as when in possession rotates between attacking and defensive midfield to either create a 3-2 build up shape or to create the shape you'd see in the midfield of a 4-3-3 DM. The other holding midfielder is a BWM who's the more defensive-minded player in the double pivot as his aim, as implied by the name, is to win the ball back which protects the defensive line from the opposition advancing. The WB is used to provide a wider option for build-up and is also used to create overloads on the right side of the opposition's defence with the IW by making forward runs down the left meanwhile the IW, on the same side, aims to run at the opposition and make threatening runs in behind to give the defence something else to worry about. The right-sided IW, who's job is to cut across the defence when he's in possession, is actually told to stay wider which can help with providing the wide option on the right as the IFB stays back and sits narrow. The AP sits in the pocket between the their defence and midfield and aims to spread the ball around and create chances. He is told to roam from position which means he can influence more of the play around different areas of the pitch. The final role is the lone AF who plays very high against the defensive line; this helps with giving the centre-backs more to think about as he is always threatening in behind: they can either prevent his runs by dropping deeper, therefore creating more space to attack in front of the defence, or they'll leave space in behind for him to make runs and score goals.