Trying to guard Kevin Durant, Melo didn't see 6'10'', 270-pound Kendrick Perkins setting a screen to free up KD. As soon as the screen was set, Anthony had no idea he was there and got drilled by Perkins. You can see a GIF of the play below.
Here's the full video of the play.
That wasn't the only thing to go wrong for Melo. He finished with just 15 points on 5-of-19 shooting while his counterpart Durant went off for 41 points. The New York Knicks ended up losing 112-100.