The Rockies had swept the Philadelphia Phillies in three games in the NL Division Series, while the Diamondbacks had swept the Chicago Cubs. The Diamondbacks had home-field advantage due to winning the division. The series marked the first time the Rockies ever advanced to the NLCS and the second time for the Diamondbacks, in the first postseason matchup between the two teams; the Rockies' only prior postseason appearance was in 1995. It was the first time that two West Division teams had ever met in the NLCS, only the second to feature expansion franchises (the first being 1986) and the first of only two postseason meetings of any kind between teams that joined MLB in the 1990s (the other meeting being the 2017 Wild Card Game between the same two clubs).