The Chargers were measured and strategic in free agency and the NFL draft, focusing heavily on the offensive and defensive lines while making subtler additions at wide receiver and in the secondary. In fact, one of their biggest offseason additions was in the coaching ranks rather than personnel. The addition of new offensive coordinator Mike McDaniel could provide as big a payoff as any player they added to the roster. Former Dolphins guard Cole Strange signed with the Chargers during the free agency period. IMAGN IMAGES via Reuters Connect McDaniel’s arrival will go a long way toward sorting out some of the key positional decisions the club faces this offseason and in training camp. Here are the three biggest battles to keep an eye on: Guard The Chargers are making wholesale changes to their interior offensive line , and both guard spots are up for grabs. Cole Strange was signed in free agency.…