Amaestrar

If the target creature’s power becomes 5 or greater as you gain control of it (perhaps because an enchantment gives creatures you control +1/+1), Wrangle will continue to resolve as normal. The creature will still be untapped and gain haste until end of turn, and you’ll still control it until end of turn.

Wrangle can target any creature with power 4 or less, even one that you already control or that is already untapped.