put somebody off their stride/stroke
put (one) off (one's) stride
To disturb, distract from, or interfere with what one is doing, such that they are unable to do it well. It really put me off my stride to have my parents watching while I worked on my painting. The boxer tried to put his opponent off his stride by getting in his face right before the fight.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
put somebody off their ˈstride/ˈstrokemake somebody take their attention off what they are doing and stop doing it so well: All sorts of things can put a player off his stroke.
Farlex Partner Idioms Dictionary © Farlex 2017