On the tactics page, under Line-up, you'll see 8 squares for reserves.
When you drag a player onto a reserve square, you are telling the game that you want this player to be substituted in, in case of injuries or suspensions, or if you set up substitution rules with an "Auto"-in substitution (see the Substitutions section).
It is very important that you always have reserves set up, since it can save you from losing matches due to sudden injuries or suspensions that occur when you are unavailable and cannot put in substitute players yourself.
Each row of reserves corresponds to a particular area on the pitch. If a player on the pitch needs to be substituted out, he will be replaced by a reserve from a reserve row corresponding to the player's position on the pitch:
- The upper 3 rows on the pitch are covered by the Forward reserves
- The middle 4 rows on the pitch are covered by the Midfielder reserves
- The bottom 3 rows on the pitch are covered by the Defender reserves
- The goalkeeper square is covered by the Keeper reserves
To make the system as simple as possible to use, these rules also apply if, for instance, an Offensive Midfielder is placed in one of the top 3 rows. In this case, his substitute will be drawn from the Forward reserves.
This also applies if a Defensive Midfielder is placed in one of the bottom 3 rows. If he is to be replaced, his substitute will be drawn from the Defender reserves.
So, it is always the player's position on the pitch that determines which row of reserves his substitute is drawn from.