In Game 5 of the series, Clark faced Cubs closer Mitch Williams with the score 1-1 in the bottom of the eighth inning. Clark singled to center field to drive in two runs, breaking the tie, eventually sending the Giants to the World Series. Clark's efforts, which included a .650 batting average and two home runs, resulted in him being named NLCS MVP. The Giants went on to face the Oakland Athletics in the 1989 World Series, but were swept. In the only World Series appearance of his career, Clark failed to contribute significantly at the plate, finishing with no runs batted in and a .250 batting average while battling tonsillitis.