As successful as the Chargers’ passing attack has been of late, Philip Rivers has rarely had a productive option at the No. 3 receiver spot. Granted, he hasn’t needed it because of the play of Vincent Jackson, Antonio Gates, Malcom Floyd and Darren Sproles (before he went to New Orleans in 2011). This year, with Jackson gone, San Diego used free agency to make up for his loss in a big way, adding Robert Meachem, Roscoe Parrish and Eddie Royal to join Floyd and 2011 draft pick Vincent Brown, giving Rivers a deep receiving corps. During minicamp, head coach Norv Turner raved about Royal, who is expected to line up in the slot. Royal has yet to return to the form of his rookie season, when he had 91 catches for 980 yards and five scores, but the Chargers’ offense could be the right ingredient for him. Meachem will start on the outside opposite Floyd, and Parrish offers another option for the slot. The speedy Parrish has to stay healthy, but he did average 50 receiving yards a game in 2010 before getting hurt.