Fitz isn't even the best WR on the team anymore
No, but he still commands the attention of the defense. There were numerous times during the Chargers game that I swear SD was playing zone on Fitz alone. There was a perfect triangle of players w/in 5yrs of Fitz when the ball was thrown and the play wasn't even going to him. It happened again with the Giants. There was one catch and 3 players tackled him.
It's been like this for years - the opponent tries to take Fitz out of the game. With a crappy QB it's and no other receivers, it's successful. Now though the Cards have other weapons and players stepping up.
Much like Dockett drawing double teams, Fitz draws defenders to him. Other players are stepping up finally.