 In 1999 , the Yankees and Red Sox faced each other for the first time in the ALCS . The Yankees were the defending World Series champions and in the midst of a run of three consecutive World Championships , while Boston had not appeared in the ALCS since 1990 . The Yankees won the first game of the ALCS against the Red Sox on a 10th @-@ inning walk @-@ off home run by Bernie Williams off Boston reliever Rod Beck . The game was the first actual postseason meeting between the rivals because the one @-@ game playoff in 1978 technically counted as a regular season game . Intensity built up due to this historic , first @-@ ever postseason meeting between the two longtime rivals . The Yankees would win the first two games at home with 7th @-@ inning comebacks . 
