The Cowboys have been hit hard by injuries this week, but one injured player is expected to be back on the field tomorrow. Safety Roy L. Williams, who had to start using his middle initial when the Cowboys traded for wide receiver Roy E. Williams this week, is expected to play Sunday for the first time since breaking his arm in Week 2 against the Eagles. “The only other time I’ve been hurt and missed a game was my junior year of high school,” Williams said. “This was horrible not to be out there and help the team. I wouldn’t wish it on anybody. Or not on anybody who is competitive and wants to play. ... You’re sitting there watching a game and you feel like, ‘Maybe if I was in there it would have been different.’ ” Williams is expected to start in a secondary that is missing two starting cornerbacks, the injured Terence Newman and the suspended Adam “Pacman” Jones.