Good point.
Certainly, when a young player is in the clubhouse and a vet like Papi of McHale says something, you're going to stop and listen-- or hopefully, you will.
Great players (and leaders) can't just say, "Stay focused!" They have to model it.
Also, learning how to stay focused is not all that easy for some. Even a great teacher or leader might not get through to everyone, while maybe some clown might say something that strikes a chord and begins a change.