The third-round draft pick out of Northern Iowa is relishing the opportunity.
''It's very exciting. I can't wait, man,'' he said after Wednesday's practice. ''I'm blessed, I'm just very glad to have this opportunity to help out the team.''
Starter Chris Johnson is out with a cracked bone where the tibia meets the knee. He was placed on the injured reserve/designated for return list and wouldn't be eligible to play again until the Super Bowl. Andre Ellington has turf toe.
Coach Bruce Arians said the Cardinals, who lead the league in offensive yards and have the NFC's second-best record at 9-2, won't change their approach to the game.
''David will just step up,'' Arians said. ''When Andre was out, David was playing a lot more early in the year. He played extremely well.''
Johnson leads the Cardinals and all NFL rookies in touchdowns with eight - four rushing, three receiving and one on a kickoff return. He scored on a one-yard run in last Sunday's 19-13 victory at San Francisco.
Johnson, who often has been the short-yardage back, has 35 carries for 139 yards and 19 catches for 241 yards.
''It's not like I just got here,'' he said. ''I've been playing in the NFL and I've been helping out our team. I feel like I'm not going to change nothing, really, just study a little bit more probably and make sure I know what I'm doing when the game comes.''
Johnson credits Chris Johnson, Ellington and quarterback Carson Palmer for preparing him for this moment.
''Don't overthink everything,'' David Johnson said. ''Just come and play my game. I don't need to try to do too much, just do my role and help out the team as much as I can.''
Johnson stands 6-foot-1 and weighs 224 pounds.
''When you look at Andre and Chris, he's probably got 30 pounds on those guys,'' Palmer said. ''Straight ahead speed, he's probably as fast as those guys. Those guys are definitely shiftier and quicker, but he can run through people and through arm tackles. Kind of a Todd Gurley-style runner - fast in the open field and just big, hard to bring down.''
As a receiver, Palmer said, the rookie is ''probably as natural a catcher as there is.''
Palmer said he and Johnson have talked about the importance of his play during the December stretch run, which includes games against Minnesota, Green Bay and Seattle.
''He understands the importance of ball security and all those things, and protection stuff,'' Palmer said, ''so he doesn't need a ton of pump-up speeches and pep talks. He doesn't need a ton of guidance.''
Chris Johnson is fourth in the NFL in rushing with 832 yards.
''Chris was having a heck of a year,'' Arians said, ''but David, given the same number of touches, I don't think would be far behind him.''
David Johnson fumbled a kickoff return to set up a St. Louis score in the Rams' 24-22 victory at Arizona on Oct. 4. But late in the game, he had a 23-yard touchdown catch.
He said he's vastly improved from that day.
''I don't get too nervous during the games anymore,'' he said. ''It's just like practice, coming out, doing what I can, trying to calm down and just let the game come to me.''
Stepfan Taylor and Kerwynn Williams are the team's other running backs. Williams was called up from the practice squad on Tuesday. It's a familiar role. He came off the practice squad last season and rushed for 100 yards on 19 carries in a victory over Kansas City.
''I'm glad he's still here,'' Palmer said. ''I think we were all kind of holding our breath when he was on the practice squad, knowing what kind of player he is, what his potential is and what he's capable of.''
Notes: Arians said Jonathan Cooper practiced and was moving well but that Ted Larsen will remain the starting right guard ''because he's playing better.'' ... Patrick Peterson is Arizona's nominee for the NFL's Man of the Year award. ... Arians said the team will look to replace David Johnson as kickoff returner because his other duties have increased so much. ...Arians said Ellington, Jerraud Powers (calf) and defensive lineman Frostee Rucker (ankle) probably will miss Sunday's game.
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