The Teferi trumps the Evocation. During your opponent's upkeep, he reveals the card, and "casts it without paying its mana cost if able". But it's not your opponent's main phase, so Teferi kicks in and says "Sorry, you're not able! Better luck next turn!".
I was hoping that someone would be able to come up with a better Wild Evocations deck, but I guess some cards are just really that hard to make good.