You don't choose a target for Yuna's Whistle at the time you cast it
She's expensive to play without shifting, so instead focus on looking for Persistent Mouse , and hope you draw into Brilliant Bosun when you're ready to close out the game
Otherwise, put a +1/+1 counter on this creature, then put the card back on top or into your graveyard. So yeah, the drawback can bite you in the ass , because your opponent can dig a bit and pump his creatures
While the deck isnt necessarily lacking one-drops, the ones it has are often fragile, even with a Curious Obsession on them
Another benefit to consider is the number of coin flips this card generates each turn
Not only does it enable you to give one of your opponents characters Reckless during their next turn, it also grants you a passive ability that punishes your opponent for banishing your characters