Affeldt struggled with injury in 2013, recording a 3.74 ERA in innings pitched. He went on the 15-day disabled list after suffering a right oblique strain on April 14. Given Affeldt's history of unusual injuries, Giants broadcaster Jon Miller joked that Affeldt suffered the injury during a sneezing fit. Affeldt clarified that he suffered the injury while pitching the night before in Chicago. He missed 50 games between July 21 and September 12 with a left groin strain. After returning for one game in September, Affeldt was shut down for the rest of the season.