We'd argue that Gronkowski is one of the five best blocking tight ends in the league. He's a difference-maker in New England's running game, and that versatility makes the Patriots' offense impossible to defend. This isn't an attack on Graham. He deserves to be high as well, but he's a more one-dimensional player.
It's not that Gronkowski is a slouch as a receiver. He just set the record for touchdowns by a tight end in a season with 17. He caught 90 passes for 1,327 yards. He just completed what was arguably greatest season ever for a tight end, but his fellow players won't even call him the best in the game.