CHARLOTTE — P.J. Walker has been in this situation before, and it's not a position without its own stress.

But as the Panthers starting quarterback this week against the Cardinals, he's still doing his best to enjoy the present.

Walker started one game for the Panthers last season against the Lions, and won. But he said Wednesday he wants to stay in the mindset he adopted when he was playing for the Houston Roughnecks the spring before.

"I'm going to just revert back to when I played in the XFL, to be honest," Walker said. "I had a lot of fun, enjoyed the moment. I'm extremely excited, but when I go out there, I want to stay extremely excited, because the guys around me need that energy, need that juice, and I want to bring it on Sunday.

"That's the most important thing; I want to bring that juice. I want to show them that juice, but also know that I need to be calm and settled when it's time to go out there and play."

He also knows that unless something changes, it's his job.

Panthers head coach Matt Rhule said that starting quarterback Sam Darnold would be out at least four weeks with a shoulder injury. Rhule said that Darnold would be placed on injured reserve at some point.

While Darnold was on the injury report after taking a hard shot against the Falcons two weeks ago, Rhule said Darnold came in Monday morning after the Patriots game with "a different pain," and further tests revealed the damage.

"Obviously, Sam is one of the toughest guys I know," Panthers running back Christian McCaffrey said. "Playing through a lot, a lot going on people don't know about. So my hat's off to him, he's a tough guy."

As you'd expect, Rhule was asked if the team planned to look outside the organization (beyond the signing of veteran backup Matt Barkley) for help at the position.

"We would obviously explore any and all options," he said. "We'll look at everything."

He wouldn't get into specifics of any particular quarterbacks who were available at the moment, after being asked specifically about former Panthers quarterback Cam Newton.

"Our job is to try to win, so we're going to talk to and evaluate whatever is possibly out there," Rhule said.

But for the scope of this week's trip to Arizona, the attention is on Walker. While he beat the Lions last year, he also threw two interceptions in the end zone that game. He also threw three picks in a relief appearance in the finale against the Saints, and they've talked to him all offseason about making better decisions with the ball.

Still, they all expressed confidence in him to add some of that sizzle to an offense that has scored one touchdown in the last three games, and McCaffrey said they believed he could do that for reasons beyond his previous start against the Lions.

"He's so much more than just that game," McCaffrey said. "I see him every day in practice; I see how he works, just talking to him about what he sees and how he sees it. Just like any position, when you have someone new come in, you want to get comfortable with him. But he's got great poise, knows the plays really well obviously, and he's a great leader."

Walker said he believes he's much more prepared than he was a year ago at this time, saying the biggest difference was "understanding the system, knowing where guys are going to be at."

Beyond that, he wants to enjoy himself and play freely, while staying within the confines of the offense and not being careless with the ball.

"Just doing my job, not doing too much," he said of his focus this week. "As a quarterback, when you feel like you can make a lot of plays, you tend to do a lot more than you need to or are asked to do, and things start to go bad. So take what's there, play the game smart, and go out and lead the guys and have fun and play great football."