Out of the players listed in the question, which one is most valuable to the team on defense?

Just based on last season, it was Shawne Merriman. The Chargers had the 25th ranked total D & 31st ranked p D in the NFL, & they still had 2 ProBowl caliber CBs in Quentin Jammer & Antonio Cromartie. Without Merriman, SD has no p rush, & it directly affected the secondary. The Chargers need him to make a big impact, because the attention other teams must commit to Merriman because of his great p rushing skills opens things up for other guys like Shaun Phillips. Not to mention his toughness & leadership skills motivate everyone on the team.