Boetsch kinda messed up when he went for a single leg from the standing position. I think in mma or a submission grappeling situation you are putting your head at major risk with the single leg. Just look what happened. I think if you are going for a shot from standing go in for the high crotch because your head is outside his hips. If it fails you can get away without getting caught easier. Single legs off your feet are much safer than standing.