A basic defensive concept in soccer is slide and slant to the ball. Figure #1(click on pic) shows the problem when the left and right backs get too wide and flat across the field. Here the other team can easily split the defense with a pass from A1 to
A2 or A1 could dribble past D1 for a break away on goal.
In order to solve this problem, the defense should remain connected in 2 ways.
1. Slide To The Ball – I’m not advocating magnet ball. However, it's alright for the defense to maintain some compactness to make dribbling and passing more difficult for the opposition. One of the problems that D2 has in Figure #1 is she does not have an inside position on A2 to prevent her from "going to goal" uncontested. In Figure #2 (click on pic), D2 slides across the field to block A2's path to the goal. In soccer, this inside defensive position is called goal side.
2. Slant To The Ball – A laterally flat defense can get split by A1 dribbling past D1 or knocking a thru ball to A2. In order to solve this problem, D2 should support D1 at a 45% angle behind and to the goal side of D1. However, don't drop back too far - WHY?
Also, slide and slant between the 2 defensive backs is used on offense as well as defense. Figure #3 (click on pic to enlarge) shows both the right and left backs moving up the field to stay connected with their teammates. The right back is in good position to support the right midfielder who has the ball. However, the left back is too flat (to the right back) in case the red team mounts a counter attack. Once again, she should slide to the middle of the field and slant back toward her own goal to be in a good defending position.
Video Clip - Here's an example of a team keeping good defensive shape by sliding and slanting as the ball moves around the field. Click the link below.
Summary
In the examples above, I showed the most classic use of slide and slant to the ball - between our 2 defensive backs. However, it also can be used between our 3 midfielders or our 2 strikers. Slide and slant (vs. standing in a straight line across the field) is all about maintaining good soccer connection and balance - just like 2 kids on a see-saw.