Usually no. For night sports under field lights, a typical external hot-shoe flash won’t meaningfully light players who are far out on the field. Flash power falls off very quickly with distance, so once your subject is more than roughly a few feet away, the benefit becomes minimal. At around 20 feet, it may help only a little, and usually only if you’re already using a high ISO.

So for most field sports, an external flash is not the solution unless you are very close to the action. In practice, you’ll usually rely on the available stadium lighting and use settings that support fast shutter speeds: raise ISO as needed and use the widest aperture your lens allows. Shooting RAW is helpful for maximizing what you can recover in post, but it won’t replace enough light for action-stopping exposure if the scene is too dim.

Bottom line: for players out on the field, a battery-powered flash is generally ineffective and not necessary.