It is the time of the season to begin grading teams' latest draft classes. Players are beginning to show who belongs in the conversation of best rookies.

According to NFL.com's Chris Wesseling, the Arizona Cardinals have a pair of the best rookies -- both of which would be considered steals.

The team's two top rookie contributors -- safety Tyrann Mathieu and running back Andre Ellington -- make Wesseling's top 15 list.

On Mathieu, who was a third round pick and even considered a risk because of his drug history, was ninth on the list.

The steal of the NFL draft, Mathieu has been an every-down asset as a slot corner, outside cornerback and deep safety. We knew about his natural playmaking instincts, but his tackling ability and run support have been just as impressive, drawing comparisons to former Vikings Pro Bowler Antoine Winfield.

Ellington, a sixth rounder, founds himself 13th on the list.

The sixth-rounder has been a big-play machine, picking up a first down 19 times on 43 touches -- good for a 44 percent conversion rate. For comparison's sake, Adrian Peterson and LeSean McCoy move the chains less than 30 percent of the time.

Unfortunately, they are the only real rookie contributors. Jonathan Cooper is on injured reserve, as is Alex Okafor. The rest have either not seen the field other than special teams or play a very small role.

However, with these two players, they appear to have found something special, at least with early returns.

You could have predicted that Mathieu could have been the biggest rookie impact on the team, but Ellington would have been a long shot, especially since he was the second running back the team took in the draft.

Where will they end up among the league's rookies by the end of the season? We have nine games left to find out.

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