On September 16, 2004, Schilling won his 20th game of 2004 for the Red Sox, becoming the fifth Boston pitcher to win 20 or more games in his first season with the team, and the first since Hall of Famer Dennis Eckersley in 1978. Schilling ended his regular season with a 21–6 record.
On October 19, 2004, Schilling won Game 6 of the 2004 American League Championship Series against the New York Yankees. Notably, he won this game playing on an injured ankle—the same injuries that contributed to his disastrous outing in Game 1 of the ALCS. These injuries were so acute that by the end of his performance that day his white sock was soaked with blood, which is now referred to as "the bloody sock". Schilling sold the "bloody sock" at auction for $92,613. The win forced a Game 7, making the Red Sox the first team in MLB history to come back from a three-games-to-none deficit. The Red Sox would go on to win Game 7 and the ALCS and make their first World Series appearance since 1986