I coached my son in U6 for 3 seasons and never used any positions but stressed "making space" and "moving with the game". We moved up to U7 this season. With bigger players, bigger goals and still no keeper, if I don't use some sort of "defender", opposing teams just shoot from half feild. Its not about "losing a game" for me, I couldn't care less about wins/losses. But without some sort of cover in the back, there's no soccer. There's just a long distance shoot-out. Although, I absolutely agree with not forcing any player to camp in the goal, the game is asking for the first stages of positioning.
When we played U7, everyone else put a sweeper in. I refused to do that. The first season, the only team that beat us could handle the ball better and play into space. My kids just couldn't compete with their soccer vision. We started loosing the second season when I let my back guy in the diamond drift back too much. I see that now - at the time I didn't. Force your game on your opponents - make them deal with a man down in their half. They'll have their forward up at your goal.
My U7 daughter's coach pushes the "sweeper" (back player in a diamond -- 4v4) up past midfield when they are on offense, and they usually either shut down the other team's attack or at least delay them enough that the wings can fall back to help. The league she plays in now doesn't permit teams to park anyone in the box when they are on offense - everyone has to be involved in the attack or the ref can give them a warning. On another note: this old thread popping up again reminded me of how miserable and whiny I was with the group she was with this time last year. Thanks to everyone for the support! We are in a much better place this year, and the girl has just turned into a soccer nut.
If you assign positions in that situation you hamper the kids ability to learn the game. Each player should have the same role. This forces them to learn about principles of play like width, depth and mobility. If they have no depth on defense, bad things happen. If they don't put immediate pressure on the ball after a transition, bad things happen. The small sided game is supposed to force them to begin thinking of themselves as part of a team, rather than playing as individuals. If you assign individual positions, they don't have to solve problems as a team.
Exactly what I was talking about. I had to trick my kids and rename it from a "sweeper" to a "rover". I told them rovers had to be up past the line and helping out on offense. And as ranova states, I wish the coach the previous year hadn't introduced the concept of sweeper in the first place and had focused on a diamond. It took me a while to accept this type of style and when I did the U6es last year, I made them believe there were no set positions.