The boot is on the other foot
Definition 1 of 1
Pro Tip 1/3Power Shift
Use it when there's a change in who has control or advantage in a situation. 
He used to be my supervisor, but with the latest promotion, the boot is on the other foot.
Pro Tip 2/3Competition Context
It's often used when discussing sports, games, or competitions that have changing winners. 
The boot is on the other foot this season, as the underdogs lead the league.
Pro Tip 3/3Not Literal
Remember it's a metaphor; it has nothing to do with actual footwear. 
When dad joined the dance class, suddenly the boot was on the other foot, and he had to follow my lead.