Here's what Bolts from the Blue said about the pick:
The draft just kind of fell right for Jabaal Sheard to be the pick here. First off, the Chargers chose a DE in the first round with Cameron Jordan, so that hole was patched and a player like Iowa's Christian Ballard no longer was an option. The pick previous saw OT Ben Ijalana go off the board, so trying to fill in for a possible Jeromey Clary departure was off the table. There still are some holes at WR to fill, but looking at the draft board and an additional second-round pick coming 11 spots later, it was worth taking a player that might not be around later, as opposed to a position that will certainly have someone worth taking later.
It makes sense. The Chargers front seven was one of the best in football and they need to add the pieces to make that the case again. I like this pick.
For the full explanation of the pick, check out Mocking The Draft.