In 2004, Affeldt was named the Royals' third starter out of Spring training. He went 0–3 with a 5.24 ERA in eight starts. His final start of came on May 18 against the Texas Rangers. Affeldt gave up five runs in four innings and received a no–decision in a 7–6 victory by the Royals. Afterwards, although his blister problems had not resurfaced, manager Tony Peña named him the Royals closer on May 21 due to poor pitching and injury problems with the other Royals closers.