Grace expects Greinke trade to have emotional impact ESPN’s Mel Kiper released his midseason NFL rookie rankings Wednesday, and a pair of Arizona Cardinals cracked the top 20. Safety Tyrann Mathieu checks in at No. 9 — and as Kiper’s No. 2 defensive back — while running back Andre Ellington is at No. 22 and is Kiper’s fourth-ranked running back. Here’s what Kiper had to say in his weekly rankings, though he says they reflect the whole season’s play and take into account things like positional value and total snap count: Derrick Hall satisfied with D-backs’ buying and selling Note: An ESPN Insider subscription is required to view the full article. 9. Tyrann Mathieu, S, Arizona Cardinals: The Cardinals’ defensive structure allows Mathieu to wreak havoc and come through with difference-making plays. And he can make those plays all over the field. He’s second on the team in tackles and tackles for loss, plus he has picked off two passes. I think the sample size is great enough that we can say Arizona got a steal. 22. Andre Ellington, RB, Arizona: Still has just that one big game (Week 8), but I expect a lot more. Run or pass threat.Mathieu, who slid to the Cardinals in the third round because a number of off-the-field incidents at LSU that led to his dismissal from the team a season after being a finalist for the 2011 Heisman Trophy, has already made a number of impact plays for the Cardinals. He forced a goal-line fumble in the season-opener in St. Louis on an acrobatic, high-effort play and made a crucial fourth-down tackle just shy of the first-down marker to seal a win against the Detroit Lions. And, as Kiper mentioned, Mathieu’s presence isn’t only felt on big plays — he’s the team’s second-leading tackler, behind only linebacker Karlos Dansby. Top Stories The 5: Takeaways from the Coyotes’ introduction of Alex Meruelo 0 Comments Share Former Cardinals kicker Phil Dawson retires Ellington’s impact has also been felt by Arizona whenever he’s on the field. The sixth-round pick from Clemson is the Cardinals’ leading rusher despite having less than half as many carries as starter Rashard Mendenhall, and he showed elite speed and vision on an 80-yard touchdown run in the Week 8 game against Atlanta that Kiper mentioned. Ellington finished that game with a season-high 154 yards on 15 carries. Though Ellington’s size will keep him from being a featured back in the NFL — he’s listed at just 5-foot-9, 199 pounds — defenses are already forced to focus on him whenever he’s on the field. In addition to his rushing ability, he’s also the Cardinals’ third-leading receiver behind Larry Fitzgerald and Michael Floyd.