Robert Nkemdiche sits out Arizona Cardinals' first practice with injury

GLENDALE, Ariz. -- First-round pick Robert Nkemdiche suffered an unspecified ankle injury upon reporting to the Arizona Cardinals early with other rookies and the team's four quarterbacks, forcing the defensive tackle to begin the official start of training camp Friday stuck on the sideline wearing a walking boot.

The 29th overall pick out of the University of Mississippi, Nkemdiche suffered the injury during a team drill, coach Bruce Arians said.

"He'll be day to day," Arians said, adding of Nmkediche's availability, "You never know with those things. Each guy, you've got to find out about them."

Nkemdiche wasn't the only one sitting out. Four players opened camp on the physically unable to perform list -- safety Tyrann Mathieu (knee), cornerback Justin Bethel (foot), defensive tackle Frostee Rucker (ankle) and linebacker Zack Wagenmann (foot).

Mathieu said he expects to be ready to practice fully in three to four weeks.

"Yeah, I think that's about right," Arians said. "He's worked real hard and we're not going to push it. We're going to make sure he's more than ready before we put him back out there."

Bethel had a setback with his foot a few weeks ago, Arians said, adding, "It's just a matter of pain tolerance still."

As for Rucker, who is entering his 11th training camp, Arians said, "Really, at this time in his career, there's not a need to go early. Just take our time with him."

One of the player who was able to participate arrived in grand style.

As a way to kick off camp with a little swag, the Cardinals and team president Michael Bidwill arranged for All-Pro cornerback Patrick Peterson land at University of Phoenix Stadium in a helicopter.

The team recently purchased the copter and plans to use it regularly to shuttle select players to and from various events during the season. On this particular day, Peterson was dropped off on the Great Lawn directly in front of the stadium and a video of his touchdown appearance was displayed on the team's social media sites.

Arians said he has seen grander and stranger entrances by players in the past, mentioning former Indianapolis Colts receiver Reggie Wayne for one.

"Reggie came in on Army truck tanks and all kinds of (things)," he said. "Reggie had a grand entrance every year."