You just had to bring up Blackmon, didn't you? He was so freaking good, and in 2013 he was looking like the top WR in the league through those first four games.
One that comes to mind is Robert Edwards with New England. RB who ran for over 1000 yards his rookie year. Then the NFL had a Rookie flag football game before the pro bowl. Same year Peyton Manning was a rookie. He blew his knee out in the game, and it was baaad. I think he came back a few years later but didn't do much.
There have been some BS RTP calls in the league this year.
But that one might have been the most BS.