In NFL Football,
It is heresy to switch quarterbacks in a game unless there is injury. Even in the relatively new "Wildcat" the quarterback generally stays on the field and another player lines up behind the center.
But if you think about it, the average score in the NFL is in the 20's. A 4 touchdown day is exceptional. A 3 touchdown day is probably about average. Usually there are at least 10 possessions.
Why not let your number 2 quarterback run a few series to see if it works? Why not after a long pass completion, have the complete 2nd team cycle on the field and have a play ready to run?
The idea that it disrupts the "flow" or rhythm is not credible. During each game very quarterback has to wait a prolonged time while the other team is on a long drive. Additionally, there are turnovers on special teams and half-time.
It is just as likely that sometimes the number 1 quarterback needs something to dirsrupt a bad rhythm.
It's just that there is CW, and it is wrong.
Baseball has this one right. The best pitchers in the league are routinely taken out whether they claim fatigue or not. There are set-up men and closers. Often the coach will have a preset routine: 7 innings from starter, 8th inning set-up, 9th inning closer; and the only reason the manager might change is if the starter is throwing a shutout, or has some kind record on the line like strikeouts or something.
It's a lesson we all need to learn. CW is there for a reason, but sometimes times and the world has change and we need to adjust.