Byron Leftwich is preparing to call regular season plays for the first time on Sunday, and there's no doubt he has several drawn up that have him very excited.

49ers coach Kyle Shanahan has been there, and he is preaching patience to Leftwich and any other coach early in his or her play-calling career. Shanahan is widely considered one of the best schemers in the NFL. He was the architect behind the Falcons' dominant offense in their 2016 Super Bowl season, which got him the job in San Francisco.

The points have been harder to come by with the 49ers because San Francisco has largely been without a star quarterback – a reminder to Shanahan that plays on paper don't always translate on the field.

"When it's your first time doing it, you have a lot of confidence, and you think everything is going to work," Shanahan said. "Sometimes you find out that it doesn't, and you have to learn from those situations. It depends a lot on your team. When I first started out, I had a pretty talented offense, and a lot of things went well and came easy. Then you go to different situations and you think it is all going to work the same and you try the same stuff, and you realize, 'Oh man, it doesn't work with this person or that person.' You have to adjust throughout your career. The more experience you get, the more you are ready for things."

Shanahan said the time for major adjustments is during the week, not during the game.

"You go out and enjoy it," Shanahan said. "You work all week, you find out what you believe in, and you don't second guess yourself in the game. You call it aggressively and do everything based off preparation that you have, and then you learn from your mistakes after."