Garruk's Uprising triggers whenever a creature with power >4 enters the battlefield. A ruling on the card says "If a creature is entering the battlefield under your control, consider static abilities to determine whether its power is 4 or greater. Spells, activated abilities, and triggered abilities can’t be used to raise the creature’s power in time to have Garruk’s Uprising’s last ability trigger or to lower it in time to stop it from triggering."
Meanwhile, a ruling on Carrion Grub says "Carrion Grub’s first ability applies only while it is on the battlefield. In all other zones, its power is 0."
In which of these scenarios will Carrion Grub trigger Garruk's Uprising?
- I have no cards in my graveyard and Garruk's Uprising in play. I play Carrion Grub, which mills a 4-power creature.
- I have a creature with >4 power in my graveyard when I play Carrion Grub.
I'm guessing that in the first case it will not trigger (because Garruk's Uprising explicitly says triggered abilities aren't in time) but I am not so sure about the second. The ruling on Carrion Grub explicitly says it has zero power until it's on the battlefield, which could be before or after Garruk's Uprising checks for a creature entering.