It just so happened that the play developed across the field, and the action ended up being in the lower left hand corner of the frame. IIRC, I was using the receiver's helmet for AF. Sometimes things are nicely centered, sometimes not. If you do everything right (exposure, shutter speed, AF, etc), you can usually perform a pretty aggressive crop like I did with these shots.
Thank goodness for high megapixel cameras and Noise Ninja and Genuine Fractals, though 
In the situation depicted in the above shots, the action is actually happening parallel to the plane of focus. What this means is, if I can nail the focus right at the beginning of getting the play in frame, I can then just concentrate of framing the shot and not mess with the AF button (the * button). Sometimes the theory here is better than the practice. I have been known to foul up a perfectly well focused series by hitting the * button in the middle of a play, when in fact I should have just left it alone. The more you shoot, the more intuitive it is when you're shooting parallel to the plane of focus.
Very rarely I will change AF points from center (like tennis). 99% of the time, I just leave it in the middle.
As for how much money there is at this level, there isn't much. As a weekend gig, it's not bad - I make more than enough to make it worth my time, but nowhere near as much as almost any full time job pulls down.
Actually, shooting youth and HS sports pays a lot better.
When I tell people how little even a double truck in SI (what a two page spread is called) pays, they are amazed. And, a double truck in SI is just about as good as editorial sports photography gets when one is a freelancer.
As for shutter lag, this can vary from camera to camera, and involves several things, including AF speed, the time it takes for the signal to go from the button to the shutter itself, as well as how long it takes the photographer to respond to his/her brain saying "mash the shutter, dang it".