CHARLOTTE – Bryan Cox, Jr., the son and namesake of a former NFL player and coach, has been around the league for a long time.

But now the undrafted rookie defensive end is on the inside, and it's a battle to stay there.

Cox, like so many others in similar situations across the NFL, is trying to prove he deserves a spot on the 53-man roster, which will be finalized on Saturday after the fourth and final preseason game.

"He's obviously got some good background and some good roots, and he's shown very well," head coach Ron Rivera said. "We'll see. Thursday is very important, not just for him, but for a number of our young guys.

"The young man has got some ability – he's still got some growing to do – but he most certainly has caught our eye and shown his improvement every week."

In the third preseason game against the Jaguars, Cox was given a chance to rotate in with the first-team defense. He responded by recording a sack in the second quarter, which led to a three-and-out.

"It can only help me, getting sacks and being productive," Cox said.

And Cox believes he helped himself by choosing to sign with the Panthers as undrafted free agent despite their depth at defensive end.

"Because Eric Washington is the best D-line coach in the league," Cox said when asked why he joined Carolina. "My pops even said that. He said he thinks I can improve under him."

Cox has seen it himself.

"I've learned a lot. He's tightened up my technique, got me coming off the ball and playing my keys," Cox said. "It's a great system. We're a penetrating front. We get off the ball and we get vertical and disrupt."

The preseason finale against the Steelers offers another opportunity to show what he's learned. And through his first training camp and three weeks of preseason, he's confident in saying he belongs.

"Yes, definitely. I've given it everything I have," Cox said. "It's either going to be good enough for this ball club or hopefully another one."