Hester visited Seattle on Wednesday but chose to return to the team that moved up to draft him in the third round in 2008.
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And whereas many teams in the NFL are phasing out the fullback position, the Chargers have added two this offseason. Last month, the team signed free agent Le'Ron McClain, who is expected to be the starting fullback. Hester will likely play extensively on special teams.
Since he joined the team, Hester has played 62 of 64 regular-season games with 23 starts.
Henderson has appeared in 44 games and started 28 between 2007 and 2010. He saw his most significant action in 2009, starting 16 games on the left side. Listed at 6-foot-7 and 300 pounds, Henderson was out of the NFL last season after reportedly arriving at Raiders camp out of shape. He kept active by playing for the Colorado Ice of the Indoor Football League.