One thing to keep in mind with sprawls is that you can combine the sprawl with a spin. In which case, you aren't always sprawling to the back but to your opponents side. This is extremely useful for those that continue to drive through their takedowns as you won't always have to meet their force full on. By allowing it to continue past you, you are now in a better position to attack.
Also, if you are in a situation where the space is enclosed and their is an obstruction behind you (like a cage fence, training room wall, or car for example), you will be able to redirect your opponent into that obstruction and still allow yourself space to move and escape. So drill the straight sprawl, and also drill sprawling out to your left and to your right.
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