Gro-A-Tog's main deck is built from creatures, instants, sorceries and lands, so Naturalize has almost nothing to hit and comes out. Pyrokinesis and Caller of the Claw don't meaningfully improve our plan against a deck full of counterspells (Counterspell, Mana Leak, Foil) and removal (Smother, Sickening Dreams), so they stay in the sideboard. The opposing deck is almost entirely blue, which makes Pyroblast and Red Elemental Blast live cards. They can counter Counterspell, Mana Leak, or Foil aimed at a key Goblin, and they can destroy Psychatog, which is blue and black. We bring in two of each in place of the dead Naturalize, the Goblin Tinkerer (no artifacts to destroy) and Goblin King (mountainwalk does nothing against a deck with no Mountains). The rest of the mainboard already applies maximum pressure, with haste from Goblin Warchief and card advantage from Goblin Ringleader and Siege-Gang Commander. That is exactly what beats a deck trying to control the board and assemble Psychatog plus discard outlets. The low curve also plays well around counterspells by presenting multiple threats per turn, and Goblin Piledriver's protection from blue makes it especially hard for this deck to answer.