DALLAS -- Notre Dame quarterback Ian Book fell in love with the place when, on a recruiting visit, a swarm of fireflies magically surrounded his family who had rented bikes to tour the campus.

"I've never seen a firefly in my life," said the junior from El Dorado Hills, California. "They were kind of going up in my face. It was kind of like this moment, 'This place is pretty awesome.' You can feel the energy on the campus."

This was the night before Notre Dame officially offered Book in 2015. The moment became transcendent when those fireflies were backlit by Touchdown Jesus.

"The tradition of ND," Book said, "you see it, you can feel it."

And sometimes, tradition be damned, reality smacks you upside the head. For all the lore surrounding Notre Dame football this week of the College Football Playoff semifinal at the Cotton Bowl, there are equal amounts candor.

Enter Irish offensive coordinator Chip Long who has not been shy about relating why Book -- a junior with one career start prior to this season -- is now the starter over a 15-game starter in senior Brandon Wimbush.

"Winning games was still feeling like we lost," said Long, who was in the middle of the decision to bench Wimbush in favor of Book going into Game 4 against Wake Forest. "We had so many points out there we felt like we were missing."

Notre Dame, then, had no problem trading fireflies for a firestorm. Officially, this is the first time two CFP teams have faced each other with starting quarterbacks who were backups at the beginning of the season.

Also officially, that's amazing. Both Clemson and Notre Dame changed quarterbacks in the middle of undefeated seasons -- and stayed undefeated.

Even Nick Saban waited until the offseason to bench his championship quarterback (Jalen Hurts).

Kelly Bryant was benched despite being 16-2 as a starter and leading Clemson to a CFP berth in 2017. Wimbush was 12-3 as a starter and had beaten Michigan in the season opener when he was shown the sideline. In both cases, the offenses took off. Notre Dame has averaged 37 points per game under Book. Lawrence has fulfilled the promise of being the nation's No. 1 recruit in 2018 with the Tigers.

"We felt like we were in a rut," said Long, who inherited Book at ND when he arrived from Memphis in 2017. "And we had too many playmakers that we had to get the ball to utilize the entire field. Our defense was playing well. We're winning games, [but] we're not scoring points."

"It got to the point where it was about the other 10 [players on offense], not just one to keep morale high," Long previously told Sports Illustrated of the switch.

This from a coach who wasn't even around the last time Notre Dame had this much quarterback upheaval. Linebacker Drue Tranquill said the Irish "split" in two factions when DeShone Kizer took over Malik Zaire in the 2016 season opener at Texas.

"It was awful. It was everything you hoped to stay away from," Tranquill explained. "It was like there were two different camps almost. Maybe the guys in the locker room wouldn't admit to that. This situation is totally different. You would think these guys are best friends, Ian and Brandon."

Those are provocative comments in a sport that doesn't readily offer up such truths. And it's not like there weren't repercussions at each school. Bryant transferred to Missouri. Wimbush is reportedly considering his transfer options while still backing up Book for Saturday's game at AT&T Stadium.

"I wouldn't say anything against Brandon," Book said. "It's what I personally wanted to bring some tempo to the offense and bring a different type of energy."

Sounds a lot like Book said something against Wimbush. The truth is that the quarterback change turned around Notre Dame's season. With Book, the offense opened up. He was more accurate than Wimbush. Book's 70 percent completion rate is fourth in the country. Book went downfield more. Of Notre Dame's first 51 scoring drives, 34 went for 70 yards or more.

Tailback Dexter Williams -- suspended for the first four games of the season -- further opened up the Notre Dame offense by rushing for almost 1,000 yards in only eight games. If Notre Dame wasn't a playoff team then, it started to become one in the moment.  

Similar success followed Clemson. Bryant replaced Deshaun Watson, then led the Tigers himself to a playoff berth in 2017. It can be argued Bryant was the difference in a two-point win at Texas A&M on Sept. 8. A couple of weeks later, he was second-string to Lawrence.

"In fairness to our team and to continue to have the culture, you have to reward production," said Tony Elliott, Clemson's co-offensive coordinator.

Tranquill added: "He's got the arm strength to throw the field out, to throw the ball across the field, which you don't see in every college quarterback. … That separates him from the majority of college quarterbacks."

Lawrence was asked if he would been OK as a backup if Bryant had held onto the job.

"I don't know if 'OK' is the right word," Lawrence said. "If I felt like he earned it, he was playing better than me then, yeah, I would have kind of wait my time."

But Bryant didn't earn it or play better than Lawrence, and here we are with another example of the modern college quarterback culture. It's basically summed up this way: "If I ain't startin', I'm departin'.

Bryant is among a group that may make this a watershed year for transfer quarterbacks. Included in that group are Georgia's Justin Fields and Alabama's Hurts (both likely transferring).

"It's been the case since I started coaching," Long said. "It's just that Twitter wasn't around. … These kids got a lot more voices in their heads than they used to, other than their parents. It's just the world they live in. I'm glad I didn't grow up in that."

It's a balancing act that, when successful, legitimizes those multi-million dollar coaching salaries. A coaching change "can really divide a culture and have people second guessing coaching staff, second guessing authority," Tranquill reiterated. 

"Yeah, it was a very difficult decision, for sure, because you've got a guy that has won for you and all that," Clemson coach Dabo Swinney said. "After four games, we felt like Trevor deserved the opportunity to start the next game. I didn't know where it would go from there."

Sometimes in strange directions. Since taking over, both Book and Lawrence have been injured to the point that their backups had to come in and win games. Wimbush started and won against Florida State on Nov. 10. Clemson back up Chase Brice had to come in and lead a come-from-behind win over Syracuse on Sept. 29 when Lawrence was injured.  

"The quarterback position is so unique, right?" Tranquill mused. "Coaches are always looking for a guy they can trust to lead the team. If you're a second-string guy, and the coach trusts the first-string guy, the odds of you playing are pretty slim."