Cade's landing isn't terribly graceful, not that that could be expected. He goes down like a sack of bricks, one hand clawing futilely at the door-- just enough to bat it almost closed instead of grabbing onto it-- and only stopping when Merrick's fist hits his face.
In all his years of combat, Cade has actually never been just... slugged in the face before. Even in spars it's been accidental or pulled, so this is as shocking as it is painful. It takes him a moment to react, in the form of trying to push Merrick off him with his good arm.