The Cardinals' highest-profile rookie looked like one on Sunday, as quarterback Kyler Murray threw three interceptions in a 23-17 loss to the Steelers.
The team's second pick in April's draft, Byron Murphy, also showed his youth.
The Cardinals' cornerback had trouble in coverage, sometimes against fellow rookie Diontae Johnson, giving up more than his fair share of yardage while getting whistled for a pair of pass interference penalties.
"He's a young player that's learning on the job," coach Kliff Kingsbury said. "He'll continue to have his ups and downs but will be a lot better for it."
Kingsbury said the Cardinals liked what they saw of Johnson in the pre-draft process, and Pittsburgh's third-round pick put his skillset on full display in the matchup. Johnson returned a punt 85 yards for a touchdown early and added six catches for 60 yards and a 2-yard touchdown. Murphy was close to knocking the football away on the score but Johnson hauled it in.
"He was out there making his plays," Murphy said. "Hats off to him for making those plays. I've just got to keep working."
Murphy was questionable for the contest with a calf injury but he started and said it was nothing serious. Murphy played primarily slot cornerback defensively, a switch from his outside cornerback role in base packages previously.
Murphy also lined up at safety a couple times, and no matter where he was, Pittsburgh quarterback Duck Hodges threw often in his direction.
"Knowing Pat (Peterson) is on the other side, obviously they're going to look at me more," Murphy said. "It's not pressure. It puts more of a chip on my shoulder. It makes me want to work harder knowing they're going to come at me. I've just got to go out there and keep playing."
VALLEJO MAKES IMPACT ON DEFENSE
Linebacker Tanner Vallejo was one of the final cuts by the Cardinals before the season, but made his way back to the practice squad in mid-November. He was elevated to the active roster this week and made a nice impact on defense.
Vallejo played in run-stopping packages and finished with five tackles, a sack and a forced fumble.
"He's just a very heady player," Kingsbury said. "We liked him in camp. It didn't work out initially, but bringing him back, he knows our defense and always seems to be around the football."
GUNTER, SWEEZY SUFFER ANKLE INJURIES
Defensive tackle Rodney Gunter left the game with an ankle injury in the third quarter and didn't return. Guard J.R. Sweezy also suffered an ankle injury and he rotated with guard Mason Cole during the contest.
"Cole, we feel comfortable with him going in, so we wanted to make sure guys were fresh and healthy," Kingsbury said.
Cole also came into the game as an extra offensive lineman for a pair of plays in the first half, even splitting out wide on one of them. The pass went the other way on a bubble screen to Larry Fitzgerald.