In a street fight, it's probably not very likely that they will put you in their Guard. However, because of the popularity of the UFC and MMA, people are seeing that position. Thus, it is a possibility that should you put them on their back, that they might wrap their legs around you, and put you in their guard, just to try to control you, and possibly hit you from there.
If this is the case, it is likely that they do not know how to use all the technical controls, submissions, and sweeps from the Guard. The reason for this is that it takes quite a bit of dedicated training, patience, practice, and discipline to learn these maneuvers and tactics.
So, if they have us in their Guard, the first thing we have to do is control their arms and keep our head low. This is to stay safe from punches. Then we push on their abdomen, and "walk our hands" backwards, and sit upright. If they try to get up, we can push on their abdomen and keep them down. After they've calmed down, we strike with our fist or elbow to their face, with lots of power. This will open up their legs. From there, we pull both of our arms in, and wrap their legs. We then hike their right leg on our left shoulder, while holding onto their left leg with our right hand. We then lean towards them and reach for their left shoulder - this is called "stacking". We then hop around to their right side, and melt our body weight down, lifting our head so we go past their legs. We end up in a Modified Side Mount, where we have our left elbow by their head, our left leg extended back, our right arm by their hip, and our right knee by their hip.
In the Modified Side Mount, we can follow them while maintaining control of them in any direction. Eventually from the Modified Side Mount, you can transition into the Full Side Mount.
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