Olympic champion Joseph Schooling on Friday (Jul 28) qualified for the men's 100m butterfly semi-finals at the FINA World Championships. Schooling clocked 51.21s at the Duna Arena in Budapest, Hungary to finish fourth overall in the heats. Fellow Singaporean Quah Zheng Wen missed out on a semi-final spot, clocking 52.13s to take 18th position. US swimmer Caeleb Dressel finished overall first in the heats after touching the wall in 50.08s. Italy's Piero Codia (51.09s) and Great Britian's James Guy (51.16s) finished second and third respectively. Dressel's effort in the heats was the quickest time for the 100m butterfly this year. The semi-final will take place later on Friday from 11.30pm (Singapore time). Schooling is favourite to win this event after he clinched Singapore's historic gold medal during the 2016 Rio Olympic Games. The 22-year-old has experienced a mixed campaign so far, breaking the Asian record twice for the 50m butterfly in the heats and the semi-finals but he missed out on a podium finish after coming in fifth in the final. Quah is still scheduled to compete in the 50m backstroke at the meet from Saturday.