Despite his struggles at the plate during the regular season, Ruiz was an integral part of the Phillies' postseason success. After the Phillies clinched the 2008 National League Championship Series, he commented that the glory of winning a crucial baseball game that clinched the series, which he had witnessed while growing up in Panama on television, "happened to me", noting the aura of the moment, and that it culminated and validated the hard work he had put in over the years. Subsequently, in game 3 of the 2008 World Series, Ruiz tapped a ground ball up the third-base line for a walk-off infield single, the first in MLB history. Ruiz noted, "I heard them cheering. And that's when I knew, 'Okay it's over' ... I'll take a win." The Phillies eventually won the World Series for the first time since 1980, doing so in five games, the last of which began on October 27 and ended on October 29 after it was suspended part-way through due to rain. For his performance in the playoffs, he earned the nickname "Señor Octubre" (Mr. October in Spanish).