Is this a lighted indoor stadium? I have heard a fairly frequent problem in such situations can be the lights, which flicker at a rate not picked up by the eye but affecting fast shutter speeds. The meter is frozen just at the moment the shutter fires, and if the flicker is timed just wrong, it changes in that split second and the exposure is off. You might try shooting in short bursts and see if the exposure varies within a burst of several shots. Another possibility might be to bracket.
This is assuming it's not just that the matrix meter has caught some highlight you didn't register, and compensated too much for it. For that you might do better with spot metering, or test several exposures at a fairly wide angle, and select one with the best balance, then stick to that with auto ISO off. You'd basically be faking an incident-light setting, since you can't actually go out into the field with an incident light meter and do it that way. This works pretty well if the lighting is uniform, but the subjects are not.
