CHARLOTTE – Christian McCaffrey has been the definition of a "good rookie" since coming to Carolina as the eighth overall pick.

49ers rookie defensive lineman Solomon Thomas – McCaffrey's former teammate and roommate at Stanford – wouldn't have expected anything else.

"That sounds like Christian," Thomas said in a conference call Wednesday afternoon. "He's always doing the right thing."

The college buddies who bonded over late-night talks and Connect Four battles will now square off Sunday in their NFL regular season debuts.

"It should be a lot of fun," McCaffrey said. "Being able to play against Solomon will be a lot of fun with him being my roommate and one of my best friends. I'm excited."

Thomas has a reason to be a little more excited. He never had an opportunity to tackle McCaffrey when they were teammates. He'll get his chance Sunday.

"We wanted to protect him and make sure he stayed healthy," Thomas said. "If I get the chance I need to take advantage of it. That would be a fun thing to talk about in the group chat."

Added McCaffrey, with a smile: "I told him it's still the same rule (as college), so hopefully he believes it."

Thomas knows tackling – or getting hands on – McCaffrey is easier said than done. He still remembers what McCaffrey did to some veteran Cardinal defenders as a freshman.

"They were doing 7-on-7 routes and he was just putting work on our senior safeties who were supposed to be some of the top in the nation," Thomas said. "Making it look like it was nothing.

"Made them look like they were in slow motion, made them look like they had slow feet. It was insane the kind of things he did as a freshman."

McCaffrey did some insane things during his first NFL training camp, generating a ton of buzz with his explosive playmaking ability as a ball-carrier and as a pass-catcher.

San Francisco head coach Kyle Shanahan knows better than most how problematic he'll be to defend.

To add another layer of connections to this story, Shanahan's father Mike coached McCaffrey's father Ed with the Broncos. Kyle Shanahan wore No. 87 in his playing days because of Ed, and the 49ers' new coach was one of the first to witness Christian's special ability.

"He played in a Pop Warner game at halftime or before a Broncos game where he just tore it up," Shanahan, who apparently used to babysit McCaffrey, recalled in a conference call. "He had unbelievable moves back then."

"I haven't studied him throughout the preseason, but I know how good of a player he is. I studied him hard coming out of college, and I've known him for a long time in my life. He's a hell of a person. He's exceptional when it comes to studying the game and having a feel for the game, and his talent is way above most people's. I know he's an issue to deal with. Anytime you have a guy who can be a running back or a receiver on any given play, that causes issues for a defense. I know it will be a challenge for us schematically and athletically to handle it."

Thomas will be one of the 49ers tasked with disrupting the line of scrimmage and stopping McCaffrey before he gets started.

For the first time, McCaffrey is his enemy on the field of battle. Like McCaffrey, Thomas is a Game of Thrones fan, so he was asked which house the Carolina running back would fall into.

"I'm sorry Christian, but I'm making him a Lannister," Thomas said, referencing the villainous family on the show. "Right now he's a Lannister for this week."

But be careful Thomas. McCaffrey is coming.