off your game
off (one's) game
Unable to perform as well as usual. She never misses that shot. She must be off her game today. Staying up late last night really put me off my game at work.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
off (or on) your gameplaying badly (or well).
Farlex Partner Idioms Dictionary © Farlex 2017