영어 Slang of the Day #4: What is a "Monday Morning Quarterback"

In the U.S., American football is, by far, the dominant sport
Perhaps the fact that Samsung is the official TV of the National Football League (NFL) may the largest single signal of Korea's economic advancement to the world.  The quarterback is the most important position on a football team.  On sports channels, like ESPN, the decisions that the quarterback makes are scrutinized from every angle.  The actual games traditionally occur on Sunday (일요일).  The analysis traditionally occurs on Mondays.

From that background, you can understand what "Monday morning quarterback" means.  It means that people, with the benefit of hindsight, freely criticize decisions, without actually being there at the time.  The term "Monday morning quarterback" is used to describe those people who may or may not have the expertise to criticize, but do so anyway.  You can use the phrase for any topic, not only American football.

Examples:
(o)  That analyst is just being a Monday morning quarterback.  He has never even played golf, and that putt was more difficult than it seemed.
(o)  It is easy for you to say:  you are a Monday morning quarterback.  Everyone is an expert after the result is known.

Notes:
This phrase is usually not used in writing.  It is quite informal.
You can say "Monday morning quarterbacking" as a noun, but it is not strictly correct.  For example, you can say "There is a lot of Monday morning quarterbacking going on in the newspapers this morning after last night's incident."  However, "quarterbacking" isn't really a noun that is widely used in any other ways.