Kyle Shanahan explains the nuances of rest-or-play question in meaningless Week 18 game

The 49ers have earned the No. 1 seed in the NFC. Like the top seeded Ravens in the AFC, the 49ers have to decide whether to play or to sit starters in Week 18.

It's not as easy as it sounds, because someone has to play in the game. And, more importantly, someone has to get ready to play in the game.

“I think it can be tough," Shanahan told reporters on Monday, "but it's not just playing, it's how much you practice and everything too. You’ve got to make sure that you prepare for games by practicing. We’ve got a game this week on Sunday. When you give guys the game off, practice changes too. That can end up hurting guys a lot and you end up just developing bad habits. I've seen it cost a lot of teams. Also, it does give some guys a chance to get healthy. When you do that and you sit people, then some of the names you guys mentioned [like Brock Purdy and Trent Williams], but then other people have got to double up and do a lot more because you only get two guys off a practice squad also. If you want to get more than two off practice squad, we’ve got to cut people on a roster and then we don't get those guys, just to get those guys up. So, it always can end up hurting. You rest players and that sometimes gets more players injured. That's all that stuff you’ve got to balance out and that's why there's not a clear-cut decision on anything. You’ve got to look at each individual, in each situation and play it out as the week goes.”

Shanahan said he's still discussing the situation with coaches, and that he'll probably discuss it with the players impacted by the decision.

The goal is to be ready for the playoffs without exposing a key player to an unnecessary injury. With the Dolphins losing pass-rusher Bradley Chubb in garbage time on Sunday, coaches like Shanahan and Ravens coach John Harbaugh might be more inclined to protect their players.

The risk, of course, is that the top seed will be caught flat-footed when going three weeks between games. The reality is that a coach is far less likely to be loudly criticized for resting and protecting starters and losing in the divisional round than for risking starters and losing one or more in a meaningless game — even if the team later wins in the playoffs.

The key is the routine. Find a way to keep doing what the team has been doing each and every week. Maybe the right balance is to get the starters ready and to give them a cameo appearance on game day.