If the batter steps across the plate without swinging then that outside corner pitch might have been outside and a ball. This is not to say that we should allow the batter to make our calls. These are just guidelines to help you. Call the glove on a curve. This is an advanced theory for levels of ball where the curves are breaking like curves.
Some umpires believe a curve can enter the strike zone and then curve down into the dirt.
I'm not going to argue about that. What I will say is that even if you believe the ball entered the strike zone you should not call this pitch in the dirt a strike. These same umpires believe a curve ball which smacks right into the center of the mitt was too high when it crossed the strike zone. Once again I will not argue physics. Just call this pitch a strike - reward that pitcher for hitting the mitt, freezing the batter and awing the crowd.