That just tells me that the Chargers feel that they did a good job getting him in the later rounds.
Unless it's required by the league (I don't really know), you don't sign a 7th round kid to a four-year deal unless you think he's going to be a solid player.
Good for David.
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"I don't get sick. I don't observe major holidays. I'm a jackhammer." - Jim Harbaugh & Dwight Schrute