Monday morning quarterback

A derogatory American expression for someone who is unfairly wise after the event; derives from American football where the quarterback position is regarded as the most influential position on the field, from where strategy or game plan is mostly dictated. Most American football games are played on a Sunday, hence the Monday morning quarterback has the benefit of hindsight or after-the-event wisdom. It is said to have been coined by Barry Wood, a star Harvard University quarterback in 1931. He used it in a literal sense but the expression soon caught on and has been used figuratively from about 1932, according to the Merriam-Webster Dictionary.