You can play the exiled card if Goblin Researcher attacked and is still in combat, has left combat, has left the battlefield, or even if combat is over.

If you control more than one card named Goblin Researcher, each one's effect is independent from the other. Specifically, attacking with one will not allow you to play the card exiled by the other.

If you exile a land card with Goblin Researcher's enters-the-battlefield ability, you may play that land only if you have any available land plays. Normally, this means you can play the land only if you haven't played a land yet that turn.

Goblin Researcher's effect doesn't change when you can play the exiled card. For example, if you exile a sorcery card, you can cast it only during your main phase when the stack is empty.

Casting an exiled card causes it to leave exile. You can't cast it multiple times.

The card Goblin Researcher exiles is exiled face up.