The Cardinals built a -game lead prior to the 1967 season All-Star break, and Gibson pitched the seventh and eighth innings of the 1967 All-Star game. Gibson then faced the Pittsburgh Pirates on July 15, when Roberto Clemente hit a line drive off Gibson's right leg. Unaware his leg had been fractured, Gibson faced three more batters before his right fibula bone snapped above the ankle. After Gibson returned on September 7, the Cardinals secured the National League pennant on September 18, games ahead of the San Francisco Giants.