rushing the passer

Is there something specific that causes a pass rusher to fall down as soon as you try and get off a block. As soon as the ball is snaped and I use the Right stick to get off a block sometimes my man falls straight on his face. I would like to know what I am doing wrong so maybe I can avoid it.

being a fat un-agile person will make them fall off there blocks or when a speedy DE trys to get around a LT thats rated 95+

I just figured that I was pressing the wrong direction at the wrong time, so I guess that I no control over it happening, I don't know if I should be releived that it isn't my fault or pissed that it will continue to happen no matter what I do... I realize it happens in the nfl but not everyother play

how you do that this kell

Release the left stick for a second, I think holding both sticks at once causes him to fall more.