Soon after returning from his injury, Hernández was called up to the major leagues by the Mariners. He made his debut on August 4, 2005, in a 3–1 loss in a road game against the Detroit Tigers. At 19 years, 118 days, he was the youngest pitcher to appear in the major leagues since José Rijo in 1984. Hernández earned his first major league win in his next outing on August 9, 2005, pitching eight shutout innings in a 1–0 victory at home over the Minnesota Twins. Over his first several starts, he registered a streak of 112 batters faced before he allowed his first extra-base hit, a double by Jermaine Dye of the Chicago White Sox.