[laravel] mencari average pada relationship one to many

Ask Saya punya 2 tabel : 1. player (id, nama) 2. scores (id, player_id, nilai)

Player.php (Model)

public function scores()
{
    return $this->hasMany('App\Scores');
}

Scores.php (Model)

public function player()
{
    return $this->belongsTo('App\Player');
}

dan querynya :

$players = Player::with('scores')->limit(20)->get();

bagaimana caranya mendapatkan rata-rata dari tabel `scores`.`nilai` ? Terima kasih