Cardinals safety Tyvon Branch also played nickel cornerback against the Raiders on Friday.

General Manager Steve Keim loves to watch the Cardinals offense fly up and down the field and score touchdowns.

But every time he does, it's a reminder of the cat-and-mouse game he's constantly playing as the roster architect on defense.

"Guys like Bruce Arians are just thinking of ways to come up with an athletic mismatch," Keim said. "Get David Johnson on this linebacker, or this safety."

The Cardinals' secondary has two of the best players in the NFL in cornerback Patrick Peterson and safety Tyrann Mathieu, so it should always be above average. In order to be elite, the whole group needs to shine, and Keim believes he made the right moves to get there this offseason.

Keim allowed starting safety Rashad Johnson and starting cornerback Jerraud Powers to walk in free agency, while safety Tyvon Branch was signed to a two-year deal and cornerback Brandon Williams was drafted in the third round. Both newcomers seem likely to have a prominent role in 2016, bringing with them one major factor.

"A lot of speed," Peterson said. "Both of those guys add a bigger athletic standpoint to the back-end for sure."

It's always risky letting veterans like Johnson and Powers leave because their high football IQ can save the defense on certain plays, but no amount of mental preparation can make a player run faster.

The Cardinals were innovators when they moved safety Deone Bucannon into an inside linebacker role, sacrificing size for speed. Now Keim hopes to add more athleticism at defensive back.

"The day and age of the 260-pound 'Mike' linebackers that go downhill and are two-down thumpers don't exist anymore," Keim said. "Today everything is so spread out, you have to have athletes."

The Cardinals' previous secondary played together for several years, and that chemistry was apparent on the field last year. There weren't very many mix-ups, and if something was askew, Johnson often pointed it out quickly enough to fix it.

Mathieu said the talent level alone of the new defensive backs brings excitement, but the unit must come together.

"I think it's going to help us out tremendously, but at the end of the day, we've got to have that chemistry," Mathieu said. "We've got to click. We've got to learn how to play with each other. We'll continue to work on that in camp and I think it will help us tremendously moving forward."

Branch has many of Mathieu's traits, in that he can play both the traditional safety role and line up at slot cornerback.

"I've been doing that my whole career, and I'm comfortable with it," Branch said.

More than the speed and athleticsm, it's that versatility which gets Keim excited. Mathieu is a rare breed who can bounce about assignments from one play to the next, and Keim believes Branch has similar tools.

Branch is a former standout in Oakland who suffered some injuries and watched his career plateau. Now healthy, Keim believes he's the exact type of player the Cardinals need.

"When we talk to our scouts, we're not looking for the big, physical safety," Keim said. "We're looking for the rangy guy who can cover in the slot, cover the three, play some nickel. Tyvon was the one guy out there that I really thought fit that mold."