Ever since Bruce Arians arrived in Arizona, he has made use of the second field during OTAs and minicamp. The concept is simple. With 90 players on the roster, and the veterans needing their time to learn, the third- and fourth-string players and others needing work head over to run the same script that the first two units run on the main field.

After the opening OTA, Arians said that meant 42 reps for each field, and significant work for the inexperienced.

"Most teams' rookies got five or six reps if they were lucky," Arians said. "Ours got 42. That's one of the ways we try to bring young players along."

Nowhere are those reps more important than at defensive back, with Patrick Peterson, Tyrann Mathieu and Justin Bethel all sidelined with injuries. The Cards are short enough that draft picks Brandon Williams and Harlan Miller, both cornerbacks, are getting their work on the main field thus far. Williams, not surprisingly, has a way to go given his inexperience at the position -- Peterson has been working with him closely in practice. But reps against receivers like Larry Fitzgerald or Michael Floyd or Smokey Brown and even guys like J.J. Nelson will quickly show what needs to be learned.

There has been much speculation about whether the Cardinals will sign another cornerback. With the versatility on hand (safeties like Tyvon Branch and Marqui Christian will likely get some work there in practice) and the second field, the Cardinals will get a good sense of just what they have at cornerback on the roster -- and whether they need to find someone else later.