Melding by picking pack

Must you have everything you need to meld without using top card in pack being picked up. Example you have two aces and 2 wildcard 2s, 3 nines, and 2 eights and 1 wildcard 2. You are picking up a pack with 8 on top. Question is. Must you have the wildcard with the eights to meld or can you put down 2 eights and add third from pile.