Former Naval Academy star running back Eric Kettani will continue his pursuit of an NFL roster spot tomorrow night, when the Washington Redskins visit the Tennessee Titans for one of the most exciting three-plus hours of sports a fan can ask for — a preseason football game. It’s been an uncommon career arc for Kettani, a lieutenant in the Navy Reserve: Averaging an impressive 5.4 yards per carry at Navy (sixth-best in school history); spending two years on active duty before signing with the New England Patriots, only to have his request for early release denied; securing that release only…