Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bc4/3...Nf6/4. Ng5/4...d5/5. exd5/5...Ne7

5...Ne7?

The Denver Variation. Also known as the Port Norris Gambit or the Llamaball Countergambit. It may seem sharp at first, but it is way too passive for Black and allows 6. d4! which exploits the bad move that Black made. However, White has to play precisely to keep the advantage. It is sometimes considered a gambit, as it sacrifices the center for a strong outpost for the knight. Still, this is strongly condemned.

Counterplay with this move

This still has some upsides. It creates a double attack on the pawn, & creates a strong position. Even though Black will play for the position in the middlegame, the endgame can have some fine positions for Black.

Summary

Even though it's arguably better than taking the "free" pawn, it's still strongly discouraged to play it.