1964 Philadelphia Phillies
On Sept. 21, slugger Johnny Callison and the Phillies led St. Louis and Cincinnati by 6 1/2 games with 12 to play. Philadelphia lost 10 in a row and lost the NL pennant to St. Louis. If the Cardinals had lost on the final day of the season, an unprecedented three-team playoff between St. Louis, the Reds and the Phillies would have resulted. Of course, the Cards won.