keep (one) on the sidelines

1. sports To keep a player from participating in a game by or as by instructing them to remain on the sidelines of the field or pitch. Oh, I have no problem keeping Robby on the sidelines for this week's game—those are the consequences for being late to practice!

2. By extension, to keep one from actively participating in something; to limit one's involvement in something. I know I was out of the office last week, but I can't believe the boss kept me on the sidelines of this new project.