Kyle Shanahan's first opponent, as the head coach of the San Francisco 49ers, was against the team he will face on Sunday, the Carolina Panthers. For Shanahan, it seemed like, after spending two seasons in the NFC South as the offensive coordinator of the Atlanta Falcons, Shanahan couldn't escape Carolina.

During that game, the parents of 49ers defensive lineman Solomon Thomas and Panthers running back Christian McCaffrey, both rookies at the time for their respective teams, sat together in the Levi's Stadium stands to watch their children in their first NFL games. McCaffrey's Panthers ended up coming out on top, which was bittersweet for the parents of the two Stanford products since there was love between the families for both of the players.

Thomas and McCaffrey were good friends. The two would have heated battles of Connect Four in college.

Yes, Connect Four.

"We'd have the scoresheet out that Christian made," Thomas said of the heated tournaments after being drafted by the 49ers. "We would just go at it. It got pretty intense. The board almost broke a couple of times."

Thomas isn't the only Niner who will probably hug McCaffrey before kickoff on Sunday. Shanahan is quite familiar with the running back, too. In fact, his connection with McCaffrey goes back a lot further than Thomas'.

"I knew Christian when he was so much younger," Shanahan told Charlotte area reporters via a conference call this week.

McCaffrey's father, by the way, is former NFL receiver Ed McCaffrey, who is best known for his time with the Denver Broncos but did win one of his three Super Bowls during his single season with San Francisco. Kyle Shanahan, of course, is the son of former Broncos head coach Mike Shanahan, so he and McCaffrey had crossed paths before.

"I just remember him always after the Broncos games being on the field after the game," Shanahan continued. "Him and all his brothers just playing tackle football out there. I remember seeing highlights of him that Ed would show us when he was like a second-grader. He looked the same then as he does now. Didn't realize it would continue to go at that big of a freak level, but I was very close with his parents.

"Ed and Lisa are really good friends of mine. His dad was my hero. He's why I wore No. 87 in college, trying to be a receiver like him. Just to watch Christian end up being the player that he is, is pretty cool."

Shanahan had a chance to draft McCaffrey, who has become a game-changing NFL running back, in his first season with the 49ers. The team used the No. 3 overall pick on Thomas, instead. McCaffrey went to the Panthers five picks later.

"It was tough, very tough, especially being an offensive coach and thinking all the fun things that you can do with a guy like that," Shanahan shared, "but we're happy how it ended up, and I'm glad that he's happy there in Carolina. It's definitely a hard feeling like I'm watching Marshall Faulk coming to town."

There were some concerns that McCaffrey's transition from the college game to the NFL might be difficult. General manager John Lynch joined KNBR on Friday morning and said he heard the chatter around the league, leading up to that draft.

"We thought long and hard about [drafting him], we really did," Lynch said. "It was more about what we felt like our team needed at the time, and we wanted to add to this D-line, so we did. But yeah, there were whispers, and he's done what he's always done — continue to prove people wrong.

"What I really respect so much of him, he came in and obviously a great pass catcher out of the backfield. But he just adds a layer, like the great ones do. Now, he's thick and strong and can break tackles. It seems like he's getting faster. Now, when he breaks it, he's a legitimate threat to go the distance on any given play."

McCaffrey ranks No. 3 among NFL running backs right now with 618 rushing yards but has also added 305 receiving yards to his total yards from scrimmage. He also has nine touchdowns (seven rushing, two receiving) this season. McCaffrey's 16 runs of 10-or-more yards this season ranks No. 4 among running backs, according to Pro Football Focus.

Shanahan knows stopping McCaffrey on Sunday will be a necessity if the 49ers hope to reach 7-0.

"You've just got to be on it," Shanahan explained. "It's not like you can just get amped up and just go hit him hard. You better make sure everybody is in their gaps and in their exact right positions. He's very smooth at how he runs. His feet are always under him. He can make violent cuts.

"He does run hard, but the thing that's scary about him is he always finds the open gap, and if you get a guy out of a gap, he will be on your middle third player faster than anyone in the league. He does a very good job of making that guy miss without breaking down. That's why he's got so many long runs this year."