Two offseasons ago, I wrote a column asking which 2016 playoff team was least likely to make the postseason in 2017. I picked the Toronto Blue Jays. I was right! The Blue Jays fell from 89 wins to 76 and missed the playoffs.
If I remember correctly, my reasoning focused on the age of a Toronto lineup that dropped from 891 runs scored in 2015 to 759 in 2016 and looked vulnerable in 2017 (when the Blue Jays scored 693 runs). The Blue Jays did not have the biggest drop in wins of the 2016 playoff teams, though.