My first pet was swapped in after the Zandalari was killed by Void Gate. It might be better to put a low level/low hp pet in first to ensure your fox is swapped in while Shadeflicker still has shattered defenses.
on the Turn 8, my little fox missed every attack and was killed. My first position random pet was a mechanical (Lil' XT) by chance. He got one shot in on the round, but killed. Mechanical was able to come back and his one attack finished off Shadeflicker.