A good teammate covers your mistake in the game and brings it up later, just the two of you.

The middle of a game is the worst possible moment for coaching. Everybody is already tense, the next play is coming, and a correction delivered in front of nine other people mostly produces defensiveness and a worse next five minutes. Covering in the moment is not dishonesty; it is choosing the right time. The conversation still has to happen, which is the part people skip once the adrenaline has gone.

Say nothing on the pitch beyond something useful. Then find them the next day, alone, and be specific about the one thing. Keep it to that one thing, and say what you got wrong yourself while you are there.