CHARLOTTE – New Panthers defensive lineman Morgan Fox learns a little more each year about how to rush the passer.

And having a close-up view of one of the best in the business didn't hurt.

The Panthers are hoping to help their third-down rush this year with the acquisition of Fox, who signed his free-agent deal last week, a rapid-fire courtship which was a new process for him.

Fox laughed and called the opening hours of the free agency period "crazy," acknowledging that for a former undrafted rookie from Division II Colorado State-Pueblo, the volley of calls and texts he was fielding last week was a new experience.

"Coming from a small school, and being undrafted, you appreciate what you got and what you were given, and it was cool to be in a position to have options, and a place that wants you because of the kind of player you are and the body of work you've put up," Fox said. "It's new now that the body of work is coming to fruition, and I have a chance to come to a place where they want me, that's exciting."

Having options is central to the team's excitement about adding Fox.

He's listed as a defensive end, but grew into an effective interior rusher for the Rams, and had six sacks last season. The Panthers see him fitting into a version of the role Efe Obada played last year, but with the way the 26-year-old has progressed in his career, they see Fox as a player on the rise with the potential for more.

Learning to do multiple things took some time for Fox, as he worked his way up from the practice squad to the active roster to a key role in the Rams defense.

That meant lining up next to some guy named Aaron Donald, himself an undersized rusher, but of a far different magnitude — and that's no offense to Fox, Donald's a different magnitude from nearly everyone.

"He's awesome," Fox said of his former teammate. "He bleeds out his level of excellence, and guys around him just elevate their game. So being around a guy like him, you learn so much, you develop so much, and feed off him to be a better player.

"He's always willing to talk to you, work through technique. There are definitely things you can take from him, but there are definitely things only he can do. I think that's one of the best things you can learn as a young player, is that you can learn a lot of things, but there's a lot of stuff that's specific to 99."

The Panthers may not have an Aaron Donald (again, only one team does), but the goal is for Fox to become an effective complement to Derrick Brown inside, as they continue to collect pieces on defense during a busy first week which saw Haason Reddick, Denzel Perryman and Rashaan Melvin added to the mix.