He's always been a little old for his leagues. I imagine what holds them back from promoting him has been the walks. But this is a case to go ahead and promote him, with the message "you look like you've been avoiding batters you're afraid of, so let's see you learn against a far better caliber of batter throughout the lineup, where you can't just walk everyone" - like at AA. He turned 24 the other day. At the current rate, if he eventually stumbles one year like most prospects do, he'll be practically 30 before he sees the majors. Make or break time.