Today’s athletics are so competitive, sometimes coaches are short-sighted. It’s easy to think only in terms of whether or not the athlete can finish playing the game, rather than what’s best for the player.
This is particularly true with young players who haven’t completed their bone growth yet. Knee injuries are especially difficult to tell what’s wrong. As you suggest, it may be best to use the standard first-aid formula: R.I.C.E. rest, ice, compression, and elevation.
Nothing should be done that could further damage the injured soft tissues. Instability from ligament damage or even bone fracture must be ruled out before returning the athlete to the field. A medical doctor should be relied upon for this kind of evaluation and diagnosis.