The Dallas Cowboys play their third preseason game Saturday at Arizona, and it’s time to start sorting out whether their newest players, such as rookie receiver Terrance Williams, are on track to contribute.For Williams, it’s a late start. The game against the Cardinals will be his first of the preseason, so the Cowboys have three games to get him ready to potentially be the No. 3 receiver.“There’s some development that has to be done,” receivers coach Derek Dooley said. “Our expectations don’t change. We expect the same from him as we do from all the veterans, but we also recognize that he is a rookie, so you have to have a little bit of patience at times.”Dooley said Williams is practicing with a mind to contribute, but what he does in the game and the season depends on what he does in practice.“The starting point is, are they doing it consistently well in practice?” Dooley said. “Then, when they’re doing it consistently well in practice, certainly they’re going to have opportunities in the game, and the more opportunities you take advantage of in a game, the more balls come your way. He’s got to do Step 1, which is get in a game and see what he can do.” 1Terrance Williams: For the third-round pick out of Baylor, this is his first game. He missed the first two games because of a concussion. The Cowboys will probably let him get going early so he can work with Tony Romo.2 Alex Tanney: The Cowboys probably won’t keep three quarterbacks, but Tanney might make them think about it. His instinct and pocket presence has impressed the Cowboys in camp. They’d like to see him work earlier in the game with a better crop of receivers.3 Plays at safety: Not so much from the backups; the competition is over. Rather, from the starters. Barry Church made plays on the ball against Dez Bryant in practice this week. Will Allen was all over the field with hits. This is a chance to take it to a game.4 Backup cornerbacks: With Morris Claiborne out, Orlando Scandrick has moved opposite Brandon Carr, leaving slot corner work available for Sterling Moore and B.W. Webb. That is a tough job. The Cowboys might find out who can do it.5 Arkin at guard: David Arkin is back in the starting lineup at left guard because of injury. But he is actually fighting for a spot on this team. He has a chance because Ron Leary and Nate Livings had knee surgery.