there was a pawn at d4 it was taken by black the knight fled and black has total control
Piece Theroy 3

A general rule of thumb is that:
- A knight is good in the opening, and doubles its worth when it gets past the 6th rank
- rooks are good in the endgame, and sometimes middlegame
so using these, you figure the advantadge is static, AKA longterm advantadge that shows bad in the opening and middlegame but then shines glorious in the endgame.
hope i could help :)
Everyone knows that knights are worth less than rooks. But if you fork the king and rook or queen and rook, and capture rook, it dosen't always give you an egde. Especailly if your knight is key in hold your pawn fort and control in the center. What do you think?