throw somebody a curveball
throw (one) a curveball
To introduce a problem piece of information that shocks, bewilders, or confounds one or makes it more difficult for one to succeed. An allusion to baseball, in which a curveball is a pitch that arcs towards the batter and is more difficult to hit. Primarily heard in US. The end of that trick always throws the audience a curveball. I love watching their faces as they desperately try to figure it out. It really threw Stu a curveball when Olivia announced she was leaving the company.
throw somebody a ˈcurveball(American English) surprise somebody with a problem, situation, question, etc. that they do not expect and which is difficult to deal with: Just when you think you have it all under control, life throws you a curve ball.
In baseball, a curveball is a ball that is difficult to hit because it does not move in a straight line.