Shanahan was on a conference call with reporters today and was asked if Lance's absence was because of a decision to give Jimmy Garoppolo every snap moving forward.
"No, I haven't made that decision," Shanahan responded. "The only time I did that, really, was Chicago week. Then Arizona, the game just didn't go the way we wanted. Going into this game, we didn't like a lot of the stuff in terms of what the Rams did, so we still had it up, but we didn't see it as changing the defense up ... and giving us too big an advantage. So, that's why we didn't go with it."
The 49ers coach dispelled the speculation that Lance's lack of reps might be due to the rookie not being familiar enough with the playbook.
"Trey's got the whole playbook in his head," Shanahan revealed. "He was able to do that in training camp. If you work at it, you're going to learn it all, but it's about going through it full speed. It's about going through it in game time, tempo, and going against blitzes, and all the stuff that can surprise you, and knowing when a play's a good play, when it's a bad play, when you've got to get out of something, when you've got to get to the number four choice in the progression as opposed to the one you practiced in the week.
"So, that just comes with experience, and he's getting more and more of it, and you can never get too much."
In the meantime, Garoppolo is playing well. On Monday night, the veteran quarterback completed 15 of 19 pass attempts for 182 yards, two touchdowns, and a passer rating of 141.7. That was the second-highest passer rating of his career (145.8 vs. Packers in 2019).
Garoppolo has earned his three highest overall Pro Football Focus grades of the season over the last three games, with his 82.1 grade against the Rams being his season-high.