The 3-4-2-1 is rarely used in soccer today. It is a variant of 3-4-3 formation and is just like it highly offensive. This formation uses 3 defenders, 4 midfielders, 2 forwards and one striker.
So what is the strength of this formation? Well, just like the 3-4-3, it is possible to use several strikers in the offense. For example; the two forwards can easily transform into striker and work higher upon the field.
This formation has also wingers that will guard your team's sidelines and support your strikers/forwards in offense.
The 3-4-2-1 formation
However, the formation has only three defenders which make it vulnerable in defense. Other negative aspect of this formation is that midfielders need to be highly active in defense. This requires a lot of energy and as a midfielder you will need to pose great conditioning abilities.
However, it doesn't matter how good condition you actually have if you don't want to put the extra effort in your defense. Keep in mind that you will have the ball at your feat approximately 2 minutes per game.
This means that you will need to do something else during the remaining 88 minutes of the game. You can either choose to stand or to spend that time by helping your team in defense.
This soccer formation is great for beating teams that have a strong midfield but have lack of strikers (for example 4-4-2 or 3-5-2). As with every other soccer formation you need to take your task seriously whether you are placed on the flank, top or in defense.
Learning different soccer formations can take you a while especially if you are new to soccer. However, once you get rid on how things are working it will be a piece of cake.