Below is a training exercise that can be used to help players develop the timing and understanding of when to make runs behind a high defensive line. In the Argentina game against Nigeria, Messi finally got his 1st goal at the 2018 FIFA World Cp and it cam from great movement and understanding between the players.
One key item to notice when developing a training session to encourage runs in behind the defense is that you need space behind the defense. In the exercise below you can see that the area of the field use is the middle 50 yards of the field. This setup allows there to be space behind the defense for the forwards and midfielders to run into.
Another key is that the area is in the middle of the field. Typically for passes in behind the defense to lead to goal scoring chance they are going to originate in the attacking half of the field. The closer the penetrating pass is to the backline the more difficult it is for the defenders to recover.
Setup: 80 by 70 yard area with a 50 x 70 yard area marked off by cones. 10 attackers vs 8 defenders and a goal keeper. Two small goals for the defending team to score into with a large goal and goal keeper for the attacking team to score against.
Organization: 10 attacking players (Blue) against 8 defending players (Red) in the middle third of the field. The attacking players attempt to play a penetrating pass behind the defending team into the final third of the field to create a goal scoring chance. The defending team must try to win the ball back in the middle third of the field and score into the mini goals.
Coaching Points: To help develop timing and understanding when making a run forward work on the movement of the forward players once they see a player receive the ball facing forward. You can see in the video of the Messi goal he starts his movement inside once he sees Banega has space and time to turn and face forward. This is a key visual cue for players to begin movement and make forward runs. Another key is for the attacking team to keep players in each of the zones of the field so that they are able to move the ball from side to side forcing the defensive team to shift and move. Once the attacking team can play forward, the forwards should make diagonal runs if the ball is in the same channel as them or forwards runs if the ball is in a different channel (notice Messi makes a forward run because Banega is in a different channel and is playing a diagonal pass).