I shot my daughters high school soccer game with the A55 and the 70-400G combo. It was a sunny enough day, although I'm ready for a warm day anytime soon.
I used the camera on "Aperture Priority" and set the aperture wide open. This allowed me to get consistent exposure when the sun moves behind a cloud of two. I always prefer Aperture Priority over Shutter because I like to shoot wide open, there is no depth of field at 400mm anyway, and this gives me the highest shutter speed even as the light drops. If you set the shutter speed first, and the light drops, the images are under exposed once the lens opens all the way up, but still isn't enough. (Confusing I know).
The only time I use the manual setting is when the light isn't going to change, such at an indoor game, full blue sky, or backlit on a full blue sky.
Anyway, I used the Sony 70-400G at this game. Having the zoom helps a bit when the play comes towards my side of the field. For most photos I'm shooting at 400mm, but along the sidelines I zoom out.
The focus on the camera will keep up with the play but sometimes has problems locking on right at the start. I use the "local" setting for focus area. If you use the wide setting the lens will focus on the closest focus point... which is usually the ground about 20 feet from the play. Switching to local solves this. You could also use the spot focus but then the players head has to be kept in the middle of the frame.
There is a delay between what the EVF sees and reality on the field, this takes a bit of getting used to, and I'm not used to it yet. It means you have to hit the shutter earlier. The shutter doesn't have any delay issues, it fires right away, it's just the EVF delay I'm having problems perfecting.
Think of it like this, you're shooting tennis, when you see the subject about to hit the ball you take the picture... but in reality the subject has already hit the ball and it's left the frame. The solution is to hold down the shutter earlier and let the play happen. It should work fine, but I haven't got it down yet.
I'll try again this week.